Closing Open Holes

Closing Open Holes

With the spread of Hackers and Hacking incidents, the time has come, when not only system administrators of servers of big companies, but also people who connect to the Internet by dialing up into their ISP, have to worry about securing their system. It really does not make much difference whether you have a static IP or a dynamic one, if your system is connected to the Internet, then there is every chance of it being attacked.

This manual is aimed at discussing methods of system security analysis and will shed light on as to how to secure your standalone (also a system connected to a LAN) system.

Open Ports: A Threat to Security?

In the Netstat Tutorial we had discussed how the netstat -a command showed the list of open ports on your system. Well, anyhow, before I move on, I would like to quickly recap the important part. So here goes, straight from the netstat tutorial:

Now, the ??a? option is used to display all open connections on the local machine. It also returns the remote system to which we are connected to, the port numbers of the remote system we are connected to (and the local machine) and also the type and state of connection we have with the remote system.

For Example,

C:\windows>netstat -a

Active Connections


 Proto  Local Address          Foreign Address              State
 TCP    ankit:1031             dwarf.box.sk:ftp                       ESTABLISHED
 TCP    ankit:1036             dwarf.box.sk:ftp-data                 TIME_WAIT
 TCP    ankit:1043             banners.egroups.com:80    FIN_WAIT_2
 TCP    ankit:1045             mail2.mtnl.net.in:pop3       TIME_WAIT
 TCP    ankit:1052             zztop.boxnetwork.net:80   ESTABLISHED
 TCP    ankit:1053             mail2.mtnl.net.in:pop3       TIME_WAIT
 UDP    ankit:1025             *:*
 UDP    ankit:nbdatagram       *:*


Now, let us take a single line from the above output and see what it stands for:

Proto  Local Address          Foreign Address              State
TCP    ankit:1031                dwarf.box.sk:ftp              ESTABLISHED

Now, the above can be arranged as below:

Protocol: TCP (This can be Transmission Control Protocol or TCP, User Datagram Protocol or UDP or sometimes even, IP or Internet Protocol.)

Local System Name: ankit (This is the name of the local system that you set during the Windows setup.)

Local Port opened and being used by this connection: 1031

Remote System: dwarf.box.sk (This is the non-numerical form of the system to which we are connected.)

Remote Port: ftp (This is the port number of the remote system dwarf.box.sk to which we are connected.)

State of Connection: ESTABLISHED

?Netstat? with the ??a? argument is normally used, to get a list of open ports on your own system i.e. on the local system. This can be particularly useful to check and see whether your system has a Trojan installed or not. Yes, most good Antiviral software are able to detect the presence of Trojans, but, we are hackers, and need to software to tell us, whether we are infected or not. Besides, it is more fun to do something manually than to simply click on the ?Scan? button and let some software do it.

The following is a list of Trojans and the port numbers which they use, if you Netstat yourself and find any of the following open, then you can be pretty sure, that you are infected.



Port 12345(TCP)                   Netbus
Port 31337(UDP)                 Back Orifice

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Now, the above tutorial resulted in a number of people raising questions like: If the 'netstat -a' command shows open ports on my system, does this mean that anyone can connect to them? Or, How can I close these open ports? How do I know if an open port is a threat to my system's security of not? Well, the answer to all these question would be clear, once you read the below paragraph:

Now, the thing to understand here is that, Port numbers are divided into three ranges:

The Well Known Ports are those from 0 through 1023. This range or ports is bound to the services running on them. By this what I mean is that each port usually has a specific service running on it. You see there is an internationally accepted Port Numbers to Services rule, (refer RFC 1700 Here) which specifies as to on what port number a particular service runs. For Example, By Default or normally FTP runs on Port 21. So if you find that Port 21 is open on a particular system, then it usually means that that particular system uses the FTP Protocol to transfer files. However, please note that some smart system administrators delibrately i.e. to fool lamers run fake services on popular ports. For Example, a system might be running a fake FTP daemon on Port 21. Although you get the same interface like the FTP daemon banner, response numbers etc, however, it actually might be a software logging your prescence and sometimes even tracing you!!!

The Registered Ports are those from 1024 through 49151. This range of port numbers is not bound to any specific service. Actually, Networking utlites like your Browser, Email Client, FTP software opens a random port within this range and starts a communication with the remote server. A port number within this range is the reason why you are able to surf the net or check your email etc.

If you find that when you give the netstat -a command, then a number of ports within this range are open, then you should probably not worry. These ports are simply opened so that you can get your software applications to do what you want them to do. These ports are opened temporarily by various applications to perform tasks. They act as a buffer transfering packets (data) received to the application and vis-a-versa. Once you close the application, then you find that these ports are closed automatically. For Example, when you type www.hotmail.com in your browser, then your browser randomly chooses a Registered Port and uses it as a buffer to communicate with the various remote servers involved.

The Dynamic and/or Private Ports are those from 49152 through 65535. This range is rarely used, and is mostly used by trojans, however some application do tend to use such high range port numbers. For Example,Sun starts their RPC ports at 32768.
So this basically brings us to what to do if you find that Netstat gives you a couple of open ports on your system:

1. Check the Trojan Port List and check if the open port matches with any of the popular ones. If it does then get a trojan Removal and remove the trojan.

2. If it doesn't or if the Trojan Remover says: No trojan found, then see if the open port lies in the registered Ports range. If yes, then you have nothing to worry, so forget about it.

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HACKING TRUTH: A common technique employed by a number of system administrators, is remapping ports. For example, normally the default port for HTTP is 80. However, the system administrator could also remap it to Port 8080. Now, if that is the case, then the homepage hosted at that server would be at:

http://domain.com:8080 instead of
http://domain.com:80

The idea behind Port Remapping is that instead of running a service on a well known port, where it can easily be exploited, it would be better to run it on a not so well known port, as the hacker, would find it more difficult to find that service. He would have to port scan high range of numbers to discover port remapping.

The ports used for remapping are usually pretty easy to remember. They are choosen keeping in mind the default port number at which the service being remapped should be running. For Example, POP by default runs on Port 110. However, if you were to remap it, you would choose any of the following: 1010, 11000, 1111 etc etc

Some sysadmins also like to choose Port numbers in the following manner: 1234,2345,3456,4567 and so on... Yet another reason as to why Port Remapping is done, is that on a Unix System to be able to listen to a port under 1024, you must have root previledges.
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Firewalls

Use of Firewalls is no longer confined to servers or websites or commerical companies. Even if you simply dial up into your ISP or use PPP (Point to Point Protocol) to surf the net, you simply cannot do without a firewall. So what exactly is a firewall?

Well, in non-geek language, a firewall is basically a shield which protects your system from the untrusted non-reliable systems connected to the Internet. It is a software which listens to all ports on your system for any attempts to open a connection and when it detects such an attempt, then it reacts according to the predefined set of rules. So basically, a firewall is something that protects the network(or systen) from the Internet. It is derived from the concept of firewalls used in vehicles which is a barrier made of fire resistant material protecting the vehicle in case of fire.

Now, for a better 'according to the bible' defination of a firewall: A firewall is best described as a software or hardware or both Hardware and Software packet filter that allows only selected packets to pass through from the Internet to your private internal network. A firewall is a system or a group of systems which guard a trusted network( The Internal Private Network from the untrusted network (The Internet.)

NOTE: This was a very brief desciption of what a firewall is, I would not be going into the details of their working in this manual.

Anyway,the term 'Firewalls', (which were generally used by companies for commerical purposes) has evolved into a new term called 'Personal Firewalls'. Now this term is basically used to refer to firewalls installed on a standalone system which may or may not be networked i.e. It usually connects to an ISP. Or in other words a personal firewall is a firewall used for personal use.

Now that you have a basic desciption as to what a firewall is, let us move on to why exactly you need to install a Firewall? Or, how can not installing a firewall pose a threat to the security of your system?

You see, when you are connected to the Internet, then you have millions of other untrusted systems connected to it as well. If somehow someone found out your IP address, then they could do probably anything to your system. They could exploit any vulnerability existing in your system, damage your data, and even use your system to hack into other computers.

Finding out someone'e IP Address is not very difficult. Anybody can find out your IP, through various Chat Services, Instant Messengers (ICQ, MSN, AOL etc), through a common ISP and numerous other ways. Infact finding out the IP Address of a specific person is not always the priority of some hackers.

What I mean to say by that is that there are a number of Scripts and utilities available which scan all IP addresses between a certain range for predefined common vulnerabilities. For Example, Systems with File Sharing Enabled or a system running an OS which is vulnerable to the Ping of Death attack etc etc As soon as a vulnerable system is found, then they use the IP to carry out the attacks.

The most common scanners look for systems with RAT's or Remote Administration Tools installed. They send a packet to common Trojan ports and display whether the victim's system has that Trojan installed or not. The 'Scan Range of IP Addresses' that these programs accept are quite wide and one can easily find a vulnerable system in the matter of minutes or even seconds.

Trojan Horses like Back Orifice provide remote access to your system and can set up a password sniffer. The combination of a back door and a sniffer is a dangerous one: The back door provides future remote access, while the sniffer may reveal important information about you like your other Passwords, Bank Details, Credit Card Numbers, Social Security Number etc If your home system is connected to a local LAN and the attacker manages to install a backdoor on it, then you probably have given the attacker the same access level to your internal network, as you have. This wouls also mean that you will have created a back door into your network that bypasses any firewall that may be guarding the front door.

You may argue with me that as you are using a dial up link to your ISP via PPP, the attacker would be able to access your machine only when you are online. Well, yes that is true, however, not completely true. Yes, it does make access to your system when you reconnect, difficult, as you have a dynamic Internet Protocol Address. But, although this provides a faint hope of protection, routine scanning of the range of IP's in which your IP lies, will more often than not reveal your current Dynamic IP and the back door will provide access to your system.

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HACKING TRUTH: Microsoft Says: War Dialer programs automatically scan for modems by trying every phone number within an exchange. If the modem can only be used for dial-out connections, a War Dialer won't discover it. However, PPP changes the equation, as it provides bidirectional transportmaking any connected system visible to scanners?and attackers.
*******************

So how do I protect myself from such Scans and unsolicitated attacks? Well, this is where Personal Firewalls come in. They just like their name suggests, protect you from unsolicitated connection probes, scans, attacks.

They listen to all ports for any connection requests received (from both legitimate and fake hosts) and sent (by applications like Browser, Email Client etc.) As soon as such an instance is recorded, it pops up a warning asking you what to do or whether to allow the connection to initiate or not. This warning message also contains the IP which is trying to initiate the connection and also the Port Number to which it is trying to connect i.e. the Port to which the packet was sent. It also protects your system from Port Scans, DOS Attacks, Vulnerability attacks etc. So basically it acts as a shield or a buffer which does not allow your system to communicate with the untrusted systems directly.

Most Personal Firewalls have extensive logging facilities which allows you to track down the attackers. Some popular firewalls are:

1.BlackICE Defender : An IDS for PC's. It's available at http://www.networkice.com.

2. ZoneAlarm: The easiest to setup and manage firewall. Get it for free at: www.zonelabs.com

Once you have installed a firewall on your system, you will often get a number of Warnings which might seem to be as if someone is trying to break into your system, however, they are actually bogus messages, which are caused by either your OS itself or due to the process called Allocation of Dynamic IP's. For a details description of these two, read on.

Many people complain that as soon as they dial into their ISP, their firewall says that such and such IP is probing Port X. What causes them?
Well, this is quite common. The cause is that somebody hung up just before you dialed in and your ISP assigned you the same IP address. You are now seeing the remains of communication with the previous person. This is most common when the person to which the IP was assigned earlier was using ICQ or chat programs, was connected to a Game Server or simply turned off his modem before his communication with remote servers was complete.

You might even get a message like: Such and Such IP is trying to initaite a Netbios Session on Port X. This again is extrememly common. The following is an explanation as to why it happens, which I picked up a couple of days ago: NetBIOS requests to UDP port 137 are the most common item you will see in your firewall reject logs. This comes about from a feature in Microsoft's Windows: when a program resolves an IP address into a name, it may send a NetBIOS query to IP address. This is part of the background radiation of the Internet, and is nothing to be concerned about.

What Causes them? On virtually all systems (UNIX, Macintosh, Windows), programs call the function 'gethostbyaddr()' with the desired address. This function will then do the appropriate lookup, and return the name. This function is part of the sockets API. The key thing to remember about gethostbyaddr() is that it is virtual. It doesn't specify how it resolves an address into a name. In practice, it will use all available mechanisms. If we look at UNIX, Windows, and Macintosh systems, we see the following techniques:

DNS in-addr.arpa PTR queries sent to the DNS server
NetBIOS NodeStatus queries sent to the IP address
lookups in the /etc/hosts file
AppleTalk over IP name query sent to the IP address
RPC query sent to the UNIX NIS server
NetBIOS lookup sent to the WINS server

Windows systems do the /etc/hosts, DNS, WINS, and NodeStatus techniques. In more excruciating detail, Microsoft has a generic system component called a naming service. All the protocol stacks in the system (NetBIOS, TCP/IP, Novel IPX, AppleTalk, Banyan, etc.) register the kinds of name resolutions they can perform. Some RPC products will likewise register an NIS naming service. When a program requests to resolve an address, this address gets passed onto the generic naming service. Windows will try each registered name resolution subsystem sequentially until it gets an answer.

(Side note: User's sometimes complained that accessing Windows servers is slow. This is caused by installing unneeded protocol stacks that must timeout first before the real protocol stack is queried for the server name.).

The order in which it performs these resolution steps for IP addresses can be configured under the Windows registry key

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\ServiceProvider.

Breaking Through Firewalls

Although Firewalls are meant to provide your complete protection from Port Scan probes etc there are several holes existing in popular firewalls, waiting to be exploited. In this issue, I will discuss a hole in ZoneAlarm Version 2.1.10 to 2.0.26, which allows the attacker to port scan the target system (Although normally it should stop such scans.)

If one uses port 67 as the source port of a TCP or UDP scan, ZoneAlarm will let the packet through and will not notify the user. This means, that one can TCP or UDP port scan a ZoneAlarm protected computer as if there were no firewall there IF one uses port 67 as the source port on the packets.

Exploit:

UDP Scan:
You can use NMap to port scan the host with the following command line:

nmap -g67 -P0 -p130-140 -sU 192.168.128.88

(Notice the -g67 which specifies source port).

TCP Scan:
You can use NMap to port scan the host with the following command line:

nmap -g67 -P0 -p130-140 -sS 192.168.128.88

(Notice the -g67 which specifies source port).


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Change Your IP In Less a Minute

Change Your Ip In Less Then 1 Minute

1. Click on "Start" in the bottom left hand corner of screen

2. Click on "Run"

3. Type in "command" and hit ok

You should now be at an MSDOS prompt screen.

4. Type "ipconfig /release" just like that, and hit "enter"

5. Type "exit" and leave the prompt

6. Right-click on "Network Places" or "My Network Places" on your desktop.

7. Click on "properties"

You should now be on a screen with something titled "Local Area Connection", or something close to that, and, if you have a network hooked up, all of your other networks.

8. Right click on "Local Area Connection" and click "properties"

9. Double-click on the "Internet Protocol (TCP/IP)" from the list under the "General" tab

10. Click on "Use the following IP address" under the "General" tab

11. Create an IP address (It doesn't matter what it is. I just type 1 and 2 until i fill the area up).

12. Press "Tab" and it should automatically fill in the "Subnet Mask" section with default numbers.

13. Hit the "Ok" button here

14. Hit the "Ok" button again

You should now be back to the "Local Area Connection" screen.

15. Right-click back on "Local Area Connection" and go to properties again.

16. Go back to the "TCP/IP" settings

17. This time, select "Obtain an IP address automatically"

tongue.gif 18. Hit "Ok"

19. Hit "Ok" again

20. You now have a new IP address

With a little practice, you can easily get this process down to 15 seconds.

P.S:

This only changes your dynamic IP address, not your ISP/IP address. If you plan on hacking a website with this trick be extremely careful, because if they try a little, they can trace it back

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check dos to see if you are infected

Check For Dos Check to see if you are infected

When you first turn on you computer (BEFORE DIALING INTO YOUR ISP),
open a MS-DOS Prompt window (start/programs MS-DOS Prompt).
Then type netstat -arn and press the Enter key.
Your screen should display the following (without the dotted lines
which I added for clarification).

-----------------------------------------------------------------------------
Active Routes:

  Network Address          Netmask  Gateway Address        Interface  Metric
        127.0.0.0        255.0.0.0        127.0.0.1        127.0.0.1      1
  255.255.255.255  255.255.255.255  255.255.255.255          0.0.0.0      1

--------------------------------------------------------------------------------

If you see anything else, there might be a problem (more on that later).
Now dial into your ISP, once you are connected;
go back to the MS-DOS Prompt and run the same command as before
netstat -arn, this time it will look similar to the following (without
dotted lines).

-------------------------------------------------------------------------------------

Active Routes:

  Network Address          Netmask  Gateway Address        Interface  Metric
          0.0.0.0          0.0.0.0    216.1.104.70    216.1.104.70      1
        127.0.0.0        255.0.0.0        127.0.0.1        127.0.0.1      1
      216.1.104.0    255.255.255.0    216.1.104.70    216.1.104.70      1
    216.1.104.70  255.255.255.255        127.0.0.1        127.0.0.1      1
    216.1.104.255  255.255.255.255    216.1.104.70    216.1.104.70      1
        224.0.0.0        224.0.0.0    216.1.104.70    216.1.104.70      1
  255.255.255.255  255.255.255.255    216.1.104.70    216.1.104.70      1

Route Table

Active Connections

  Proto  Local Address          Foreign Address        State
  TCP    0.0.0.0:0              0.0.0.0:0              LISTENING
  TCP    216.1.104.70:137      0.0.0.0:0              LISTENING
  TCP    216.1.104.70:138      0.0.0.0:0              LISTENING
  TCP    216.1.104.70:139      0.0.0.0:0              LISTENING
  UDP    216.1.104.70:137      *:*      

--------------------------------------------------------------------------------

What you are seeing in the first section (Active Routes) under the heading of
Network Address are some additional lines. The only ones that should be there
are ones belonging to your ISP (more on that later). In the second section
(Route Table) under Local Address you are seeing the IP address that your ISP
assigned you (in this example 216.1.104.70).

The numbers are divided into four dot notations, the first three should be
the same for both sets, while in this case the .70 is the unique number
assigned for THIS session. Next time you dial in that number will more than
likely be different.

To make sure that the first three notation are as they should be, we will run
one more command from the MS-DOS window.
From the MS-DOS Prompt type tracert /www.yourispwebsite.com or .net
or whatever it ends in. Following is an example of the output you should see.

---------------------------------------------------------------------------------------

Tracing route to /www.motion.net [207.239.117.112]over a maximum of 30 hops: 
1  128 ms  2084 ms  102 ms  chat-port.motion.net [216.1.104.4]
2  115 ms  188 ms  117 ms  chat-core.motion.net [216.1.104.1]
3  108 ms  116 ms  119 ms  www.motion.net [207.239.117.112]
Trace complete.

------------------------------------------------------------------------------------------

You will see that on lines with the 1 and 2 the first three notations of the
address match with what we saw above, which is a good thing. If it does not,
then some further investigation is needed.

If everything matches like above, you can almost breath easier. Another thing
which should you should check is programs launched during startup. To find
these, Click start/programs/startup, look at what shows up. You should be
able to recognize everything there, if not, once again more investigation is
needed.

-------------------------------------------------------------------------------------------

Now just because everything reported out like we expected (and demonstrated
above) we still are not out of the woods. How is this so, you ask? Do you use
Netmeeting? Do you get on IRC (Internet Relay Chat)? Or any other program
that makes use of the Internet. Have you every recieved an email with an
attachment that ended in .exe? The list goes on and on, basically anything
that you run could have become infected with a trojan. What this means, is
the program appears to do what you expect, but also does just a little more.
This little more could be blasting ebay.com or one of the other sites that
CNNlive was talking about.

What can you do? Well some anti-virus software will detect some trojans.
Another (tedious) thing is to start each of these "extra" Internet programs
one at a time and go through the last two steps above, looking at the routes
and connection the program uses. However, the tricky part will be figuring
out where to tracert to in order to find out if the addresses you see in
step 2 are "safe" or not. I should forewarn you, that running tracert after
tracert, after tracert might be considered "improper" by your ISP. The steps
outlined above may not work exactly as I have stated depending upon your ISP,
but with a true ISP it should work. Finally, this advise comes with NO
warranty and by following my "hints' you implicitly release me from ANY and
ALL liability which you may incur.


 Other options

Display protocol statistics and current TCP/IP network connections.
Netstat [-a] [-e] [-n] [-s] [-p proto] [-r] [intervals]

-a.. Display all connections and listening ports.
-e.. Display Ethernet statistics. This may be combined with the -s option.
-n.. Diplays address and port numbers in the numerical form.
-p proto..Shows connections for the protocol specified by proto; proto may be
TCP or UDP. If used with the -s option to display per-protocol statistics,
proto may be TCP, UDP, of IP.
-r.. Display the routing table.
-s.. Display per-protocol statistics. By default, statistics are shown for TCP
UDP and IP; the -p option may be used to specify a subset of the default
interval..Redisplay selected statistics, pausing intervals seconds between each
display. If omitted. netstat will print the current configuration information
once

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Configuring Bulletproof FTP Server

Configuring your Bulletproof FTP Server Tutorial

I thought that perhaps this tutorial might be pretty helpful for those interested in knowing how to configure their Bulletproof FTP Server that don't already know how... Here's how to get started…

This is for the Bulletproof FTP Server 2.10. However, It should work fine on most following versions as well.

I'm assuming you have it installed and cracked.

Basics
1. Start the program.
2. Click on Setup > Main > General from the pull-down menu.
3. Enter your server name into the 'Server Name' box. Under Connection set the “Max number of users" to any number. This is the limit as to how many users can be on your sever at any time.
4. Click on the 'options' tab of that same panel (on the side)
5. Look at the bottom, under IP Options. Put a check in the box “Refuse Multiple Connections from the same IP”. This will prevent one person from blocking your FTP to others.
6. Also put a check in the 'Blocked Banned IP (instead of notifying client). VERY IMPORTANT! If somebody decides to 'Hammer' (attempt to login numerous times VERY quickly) your server/computer may CRASH if you don't enable this.
7. Click on the 'advanced' tab
8. At the bottom again look at the 'hammering area'
9. Enable 'anti-hammer' and 'do not reply to people hammering' Set it for the following: Block IP 120 min if 5 connections in 60 sec. You can set this at whatever you want to but that is pretty much a standard Click 'OK'

Adding Users
11. Setup > User accounts form pull-down.
12. Right click in the empty 'User Accounts' area on the right: choose 'Add'
13. Enter account name. (ie: logon name)
14. In the 'Access rights' box right click: choose ‘Add’.
15. Browse until you find the directory (folder) you want to share. In the right column you will see a bunch of checkboxes. Put a check in the following ones: Read, Write, Append, Make, List, and +Subdirs. Press 'select'.
16. Enter a password for your new FTP account.
17. Click on 'Miscellaneous' in the left column. Make sure 'Enable Account' is selected. Enable 'Max Number of Users' set it at a number other than zero. 1 for a personal account and more that one for a group account. Enable 'Max. no. of connects per IP' set it at 1

18. Under 'Files' enable 'show relative path' this is a security issue. A FTP client will now not be able to see the ENTIRE path of the FTP. It will only see the path from the main directory. Hide hidden flies as well.
Put a tick in both of these.

Advanced:
You don't need to do any of this stuff, but It will help tweak your server and help you maintain order on it. All of the following will be broken down into small little areas that will tell you how to do one thing at a time.

Changing the Port
The default port is always 21, but you can change this. Many ISPs will routinely do a scan of its own users to find a ftp server, also when people scan for pubs they may scan your IP, thus finding your ftp server. If you do decide to change it many suggest that you make the port over 10,000.
1. Setup > Main > General
2. In the 'Connection' Area is a setting labeled 'Listen on Port Number:'
3. Make it any number you want. That will be your port number.
4. Click 'OK'

Making an 'Upload Only' or 'Download Only' ftp server.
This is for the entire SERVER, not just a user.
1. Setup > Main > Advanced
2. In the advanced window you will have the following options: uploads and downloads, downloads only, and uploads only. By default upload and download will be checked. Change it to whatever you want.
3. Click 'OK’


While you are running your server, usually you will end up spending more time at your computer than you normally do. Don't be afraid to ban IP's. Remember, on your FTP you do as you want.

When you are online you must also select the open server button next to the on-line button which is the on-line Button

You also have to use the actual Numbered ip Address ie: 66.250.216.67

Or even Better yet, get a no-ip.com address

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Band-Width

Band-Width

Band-width Explained

Most hosting companies offer a variety of bandwidth options in their plans. So exactly what is bandwidth as it relates to web hosting? Put simply, bandwidth is the amount of traffic that is allowed to occur between your web site and the rest of the internet. The amount of bandwidth a hosting company can provide is determined by their network connections, both internal to their data center and external to the public internet.

Network Connectivity

The internet, in the most simplest of terms, is a group of millions of computers connected by networks. These connections within the internet can be large or small depending upon the cabling and equipment that is used at a particular internet location. It is the size of each network connection that determines how much bandwidth is available. For example, if you use a DSL connection to connect to the internet, you have 1.54 Mega bits (Mb) of bandwidth. Bandwidth therefore is measured in bits (a single 0 or 1). Bits are grouped in bytes which form words, text, and other information that is transferred between your computer and the internet.

If you have a DSL connection to the internet, you have dedicated bandwidth between your computer and your internet provider. But your internet provider may have thousands of DSL connections to their location. All of these connection aggregate at your internet provider who then has their own dedicated connection to the internet (or multiple connections) which is much larger than your single connection. They must have enough bandwidth to serve your computing needs as well as all of their other customers. So while you have a 1.54Mb connection to your internet provider, your internet provider may have a 255Mb connection to the internet so it can accommodate your needs and up to 166 other users (255/1.54).

Traffic

A very simple analogy to use to understand bandwidth and traffic is to think of highways and cars. Bandwidth is the number of lanes on the highway and traffic is the number of cars on the highway. If you are the only car on a highway, you can travel very quickly. If you are stuck in the middle of rush hour, you may travel very slowly since all of the lanes are being used up.

Traffic is simply the number of bits that are transferred on network connections. It is easiest to understand traffic using examples. One Gigabyte is 2 to the 30th power (1,073,741,824) bytes. One gigabyte is equal to 1,024 megabytes. To put this in perspective, it takes one byte to store one character. Imagine 100 file cabinets in a building, each of these cabinets holds 1000 folders. Each folder has 100 papers. Each paper contains 100 characters - A GB is all the characters in the building. An MP3 song is about 4MB, the same song in wav format is about 40MB, a full length movie can be 800MB to 1000MB (1000MB = 1GB).

If you were to transfer this MP3 song from a web site to your computer, you would create 4MB of traffic between the web site you are downloading from and your computer. Depending upon the network connection between the web site and the internet, the transfer may occur very quickly, or it could take time if other people are also downloading files at the same time. If, for example, the web site you download from has a 10MB connection to the internet, and you are the only person accessing that web site to download your MP3, your 4MB file will be the only traffic on that web site. However, if three people are all downloading that same MP at the same time, 12MB (3 x 4MB) of traffic has been created. Because in this example, the host only has 10MB of bandwidth, someone will have to wait. The network equipment at the hosting company will cycle through each person downloading the file and transfer a small portion at a time so each person's file transfer can take place, but the transfer for everyone downloading the file will be slower. If 100 people all came to the site and downloaded the MP3 at the same time, the transfers would be extremely slow. If the host wanted to decrease the time it took to download files simultaneously, it could increase the bandwidth of their internet connection (at a cost due to upgrading equipment).

Hosting Bandwidth

In the example above, we discussed traffic in terms of downloading an MP3 file. However, each time you visit a web site, you are creating traffic, because in order to view that web page on your computer, the web page is first downloaded to your computer (between the web site and you) which is then displayed using your browser software (Internet Explorer, Netscape, etc.) . The page itself is simply a file that creates traffic just like the MP3 file in the example above (however, a web page is usually much smaller than a music file).

A web page may be very small or large depending upon the amount of text and the number and quality of images integrated within the web page. For example, the home page for CNN.com is about 200KB (200 Kilobytes = 200,000 bytes = 1,600,000 bits). This is typically large for a web page. In comparison, Yahoo's home page is about 70KB.

How Much Bandwidth Is Enough?

It depends (don't you hate that answer). But in truth, it does. Since bandwidth is a significant determinant of hosting plan prices, you should take time to determine just how much is right for you. Almost all hosting plans have bandwidth requirements measured in months, so you need to estimate the amount of bandwidth that will be required by your site on a monthly basis

If you do not intend to provide file download capability from your site, the formula for calculating bandwidth is fairly straightforward:

Average Daily Visitors x Average Page Views x Average Page Size x 31 x Fudge Factor

If you intend to allow people to download files from your site, your bandwidth calculation should be:

[(Average Daily Visitors x Average Page Views x Average Page Size) +
(Average Daily File Downloads x Average File Size)] x 31 x Fudge Factor

Let us examine each item in the formula:

Average Daily Visitors - The number of people you expect to visit your site, on average, each day. Depending upon how you market your site, this number could be from 1 to 1,000,000.

Average Page Views - On average, the number of web pages you expect a person to view. If you have 50 web pages in your web site, an average person may only view 5 of those pages each time they visit.

Average Page Size - The average size of your web pages, in Kilobytes (KB). If you have already designed your site, you can calculate this directly.

Average Daily File Downloads - The number of downloads you expect to occur on your site. This is a function of the numbers of visitors and how many times a visitor downloads a file, on average, each day.

Average File Size - Average file size of files that are downloadable from your site. Similar to your web pages, if you already know which files can be downloaded, you can calculate this directly.

Fudge Factor - A number greater than 1. Using 1.5 would be safe, which assumes that your estimate is off by 50%. However, if you were very unsure, you could use 2 or 3 to ensure that your bandwidth requirements are more than met.

Usually, hosting plans offer bandwidth in terms of Gigabytes (GB) per month. This is why our formula takes daily averages and multiplies them by 31.

Summary

Most personal or small business sites will not need more than 1GB of bandwidth per month. If you have a web site that is composed of static web pages and you expect little traffic to your site on a daily basis, go with a low bandwidth plan. If you go over the amount of bandwidth allocated in your plan, your hosting company could charge you over usage fees, so if you think the traffic to your site will be significant, you may want to go through the calculations above to estimate the amount of bandwidth required in a hosting plan.

Setting Up A Ftp

 Setting Up A Ftp

Well, since many of us have always wondered this, here it is. Long and drawn out. Also, before attempting this, realize one thing; You will have to give up your time, effort, bandwidth, and security to have a quality ftp server.

That being said, here it goes. First of all, find out if your IP (Internet Protocol) is static (not changing) or dynamic (changes everytime you log on). To do this, first consider the fact if you have a dial up modem. If you do, chances are about 999 999 out of 1 000 000 that your IP is dynamic. To make it static, just go to a place like h*tp://www.myftp.org/ to register for a static ip address.

You'll then need to get your IP. This can be done by doing this:

Going to Start -> Run -> winipcfg or www.ask.com and asking 'What is my IP?'

After doing so, you'll need to download an FTP server client. Personally, I'd recommend G6 FTP Server, Serv-U FTPor Bullitproof v2.15 all three of which are extremely reliable, and the norm of the ftp world.

You can download them on this site: h*tp://www.liaokai.com/softw_en/d_index.htm

First, you'll have to set up your ftp. For this guide, I will use step-by-step instructions for G6. First, you'll have to go into 'Setup -> General'. From here, type in your port # (default is 21). I recommend something unique, or something a bit larger (ex: 3069). If you want to, check the number of max users (this sets the amount of simultaneous maximum users on your server at once performing actions - The more on at once, the slower the connection and vice versa).

The below options are then chooseable:

-Launch with windows

-Activate FTP Server on Start-up

-Put into tray on startup

-Allow multiple instances

-Show "Loading..." status at startup

-Scan drive(s) at startup

-Confirm exit

You can do what you want with these, as they are pretty self explanatory. The scan drive feature is nice, as is the 2nd and the last option. From here, click the 'options' text on the left column.

To protect your server, you should check 'login check' and 'password check', 'Show relative path (a must!)', and any other options you feel you'll need. After doing so, click the 'advanced' text in the left column. You should then leave the buffer size on the default (unless of course you know what you're doing ), and then allow the type of ftp you want.

Uploading and downloading is usually good, but it's up to you if you want to allow uploads and/or downloads. For the server priority, that will determine how much conventional memory will be used and how much 'effort' will go into making your server run smoothly.

Anti-hammering is also good, as it prevents people from slowing down your speed. From here, click 'Log Options' from the left column. If you would like to see and record every single command and clutter up your screen, leave the defaults.

But, if you would like to see what is going on with the lowest possible space taken, click 'Screen' in the top column. You should then check off 'Log successful logins', and all of the options in the client directry, except 'Log directory changes'. After doing so, click 'Ok' in the bottom left corner.

You will then have to go into 'Setup -> User Accounts' (or ctrl & u). From here, you should click on the right most column, and right click. Choose 'Add', and choose the username(s) you would like people to have access to.

After giving a name (ex: themoonlanding), you will have to give them a set password in the bottom column (ex: wasfaked). For the 'Home IP' directory, (if you registered with a static server, check 'All IP Homes'. If your IP is static by default, choose your IP from the list. You will then have to right click in the very center column, and choose 'Add'.

From here, you will have to set the directory you want the people to have access to. After choosing the directory, I suggest you choose the options 'Read', 'List', and 'Subdirs', unless of course you know what you're doing . After doing so, make an 'upload' folder in the directory, and choose to 'add' this folder seperately to the center column. Choose 'write', 'append', 'make', 'list', and 'subdirs'. This will allow them to upload only to specific folders (your upload folder).

Now click on 'Miscellaneous' from the left column. Choose 'enable account', your time-out (how long it takes for people to remain idle before you automatically kick them off), the maximum number of users for this name, the maximum number of connections allowed simultaneously for one ip address, show relative path (a must!), and any other things at the bottom you'd like to have. Now click 'Ok'.

**Requested**

From this main menu, click the little boxing glove icon in the top corner, and right click and unchoose the hit-o-meter for both uploads and downloads (with this you can monitor IP activity). Now click the lightning bolt, and your server is now up and running.

Post your ftp info, like this:

213.10.93.141 (or something else, such as: 'f*p://example.getmyip.com')

User: *** (The username of the client)

Pass: *** (The password)

Port: *** (The port number you chose)

So make a FTP and join the FTP section

Listing The Contents Of A Ftp:

Listing the content of a FTP is very simple.

You will need FTP Content Maker, which can be downloaded from here:

ht*p://www.etplanet.com/download/application/FTP%20Content%20Maker%201.02.zip

1. Put in the IP of the server. Do not put "ftp://" or a "/" because it will not work if you do so.

2. Put in the port. If the port is the default number, 21, you do not have to enter it.

3. Put in the username and password in the appropriate fields. If the login is anonymous, you do not have to enter it.

4. If you want to list a specific directory of the FTP, place it in the directory field. Otherwise, do not enter anything in the directory field.

5. Click "Take the List!"

6. After the list has been taken, click the UBB output tab, and copy and paste to wherever you want it.

If FTP Content Maker is not working, it is probably because the server does not utilize Serv-U Software.

If you get this error message:

StatusCode = 550

LastResponse was : 'Unable to open local file test-ftp'

Error = 550 (Unable to open local file test-ftp)

Error = Unable to open local file test-ftp = 550

Close and restart FTP Content Maker, then try again.

error messages:

110 Restart marker reply. In this case, the text is exact and not left to the particular implementation; it must read: MARK yyyy = mmmm Where yyyy is User-process data stream marker, and mmmm server's equivalent marker (note the spaces between markers and "=").

120 Service ready in nnn minutes.

125 Data connection already open; transfer starting.

150 File status okay; about to open data connection.

200 Command okay.

202 Command not implemented, superfluous at this site.

211 System status, or system help reply.

212 Directory status.

213 File status.

214 Help message. On how to use the server or the meaning of a particular non-standard command. This reply is useful only to the human user.

215 NAME system type. Where NAME is an official system name from the list in the Assigned Numbers document.

220 Service ready for new user.

221 Service closing control connection. Logged out if appropriate.

225 Data connection open; no transfer in progress.

226 Closing data connection. Requested file action successful (for example, file transfer or file abort).

227 Entering Passive Mode (h1,h2,h3,h4,p1,p2).

230 User logged in, proceed.

250 Requested file action okay, completed.

257 "PATHNAME" created.

331 User name okay, need password.

332 Need account for login.

350 Requested file action pending further information.

421 Too many users logged to the same account

425 Can't open data connection.

426 Connection closed; transfer aborted.

450 Requested file action not taken. File unavailable (e.g., file busy).

451 Requested action aborted: local error in processing.

452 Requested action not taken. Insufficient storage space in system.

500 Syntax error, command unrecognized. This may include errors such as command line too long.

501 Syntax error in parameters or arguments.

502 Command not implemented.

503 Bad sequence of commands.

504 Command not implemented for that parameter.

530 Not logged in.

532 Need account for storing files.

550 Requested action not taken. File unavailable (e.g., file not found, no access).

551 Requested action aborted: page type unknown.

552 Requested file action aborted. Exceeded storage allocation (for current directory or dataset).

553 Requested action not taken. File name not allowed.

 Active FTP vs. Passive FTP, a Definitive Explanation

Introduction

One of the most commonly seen questions when dealing with firewalls and other Internet connectivity issues is the difference between active and passive FTP and how best to support either or both of them. Hopefully the following text will help to clear up some of the confusion over how to support FTP in a firewalled environment.

This may not be the definitive explanation, as the title claims, however, I've heard enough good feedback and seen this document linked in enough places to know that quite a few people have found it to be useful. I am always looking for ways to improve things though, and if you find something that is not quite clear or needs more explanation, please let me know! Recent additions to this document include the examples of both active and passive command line FTP sessions. These session examples should help make things a bit clearer. They also provide a nice picture into what goes on behind the scenes during an FTP session. Now, on to the information...

The Basics

FTP is a TCP based service exclusively. There is no UDP component to FTP. FTP is an unusual service in that it utilizes two ports, a 'data' port and a 'command' port (also known as the control port). Traditionally these are port 21 for the command port and port 20 for the data port. The confusion begins however, when we find that depending on the mode, the data port is not always on port 20.

Active FTP

In active mode FTP the client connects from a random unprivileged port (N > 1024) to the FTP server's command port, port 21. Then, the client starts listening to port N+1 and sends the FTP command PORT N+1 to the FTP server. The server will then connect back to the client's specified data port from its local data port, which is port 20.

From the server-side firewall's standpoint, to support active mode FTP the following communication channels need to be opened:

FTP server's port 21 from anywhere (Client initiates connection)

FTP server's port 21 to ports > 1024 (Server responds to client's control port)

FTP server's port 20 to ports > 1024 (Server initiates data connection to client's data port)

FTP server's port 20 from ports > 1024 (Client sends ACKs to server's data port)

In step 1, the client's command port contacts the server's command port and sends the command PORT 1027. The server then sends an ACK back to the client's command port in step 2. In step 3 the server initiates a connection on its local data port to the data port the client specified earlier. Finally, the client sends an ACK back as shown in step 4.

The main problem with active mode FTP actually falls on the client side. The FTP client doesn't make the actual connection to the data port of the server--it simply tells the server what port it is listening on and the server connects back to the specified port on the client. From the client side firewall this appears to be an outside system initiating a connection to an internal client--something that is usually blocked.

Active FTP Example

Below is an actual example of an active FTP session. The only things that have been changed are the server names, IP addresses, and user names. In this example an FTP session is initiated from testbox1.slacksite.com (192.168.150.80), a linux box running the standard FTP command line client, to testbox2.slacksite.com (192.168.150.90), a linux box running ProFTPd 1.2.2RC2. The debugging (-d) flag is used with the FTP client to show what is going on behind the scenes. Everything in red is the debugging output which shows the actual FTP commands being sent to the server and the responses generated from those commands. Normal server output is shown in black, and user input is in bold.

There are a few interesting things to consider about this dialog. Notice that when the PORT command is issued, it specifies a port on the client (192.168.150.80) system, rather than the server. We will see the opposite behavior when we use passive FTP. While we are on the subject, a quick note about the format of the PORT command. As you can see in the example below it is formatted as a series of six numbers separated by commas. The first four octets are the IP address while the second two octets comprise the port that will be used for the data connection. To find the actual port multiply the fifth octet by 256 and then add the sixth octet to the total. Thus in the example below the port number is ( (14*256) + 178), or 3762. A quick check with netstat should confirm this information.

testbox1: {/home/p-t/slacker/public_html} % ftp -d testbox2

Connected to testbox2.slacksite.com.

220 testbox2.slacksite.com FTP server ready.

Name (testbox2:slacker): slacker

---> USER slacker

331 Password required for slacker.

Password: TmpPass

---> PASS XXXX

230 User slacker logged in.

---> SYST

215 UNIX Type: L8

Remote system type is UNIX.

Using binary mode to transfer files.

ftp> ls

ftp: setsockopt (ignored): Permission denied

---> PORT 192,168,150,80,14,178

200 PORT command successful.

---> LIST

150 Opening ASCII mode data connection for file list.

drwx------ 3 slacker users 104 Jul 27 01:45 public_html

226 Transfer complete.

ftp> quit

---> QUIT

221 Goodbye.

Passive FTP

In order to resolve the issue of the server initiating the connection to the client a different method for FTP connections was developed. This was known as passive mode, or PASV, after the command used by the client to tell the server it is in passive mode.

In passive mode FTP the client initiates both connections to the server, solving the problem of firewalls filtering the incoming data port connection to the client from the server. When opening an FTP connection, the client opens two random unprivileged ports locally (N > 1024 and N+1). The first port contacts the server on port 21, but instead of then issuing a PORT command and allowing the server to connect back to its data port, the client will issue the PASV command. The result of this is that the server then opens a random unprivileged port (P > 1024) and sends the PORT P command back to the client. The client then initiates the connection from port N+1 to port P on the server to transfer data.

From the server-side firewall's standpoint, to support passive mode FTP the following communication channels need to be opened:

FTP server's port 21 from anywhere (Client initiates connection)

FTP server's port 21 to ports > 1024 (Server responds to client's control port)

FTP server's ports > 1024 from anywhere (Client initiates data connection to random port specified by server)

FTP server's ports > 1024 to remote ports > 1024 (Server sends ACKs (and data) to client's data port)

In step 1, the client contacts the server on the command port and issues the PASV command. The server then replies in step 2 with PORT 2024, telling the client which port it is listening to for the data connection. In step 3 the client then initiates the data connection from its data port to the specified server data port. Finally, the server sends back an ACK in step 4 to the client's data port.

While passive mode FTP solves many of the problems from the client side, it opens up a whole range of problems on the server side. The biggest issue is the need to allow any remote connection to high numbered ports on the server. Fortunately, many FTP daemons, including the popular WU-FTPD allow the administrator to specify a range of ports which the FTP server will use. See Appendix 1 for more information.

The second issue involves supporting and troubleshooting clients which do (or do not) support passive mode. As an example, the command line FTP utility provided with Solaris does not support passive mode, necessitating a third-party FTP client, such as ncftp.

With the massive popularity of the World Wide Web, many people prefer to use their web browser as an FTP client. Most browsers only support passive mode when accessing ftp:// URLs. This can either be good or bad depending on what the servers and firewalls are configured to support.

Passive FTP Example

Below is an actual example of a passive FTP session. The only things that have been changed are the server names, IP addresses, and user names. In this example an FTP session is initiated from testbox1.slacksite.com (192.168.150.80), a linux box running the standard FTP command line client, to testbox2.slacksite.com (192.168.150.90), a linux box running ProFTPd 1.2.2RC2. The debugging (-d) flag is used with the FTP client to show what is going on behind the scenes. Everything in red is the debugging output which shows the actual FTP commands being sent to the server and the responses generated from those commands. Normal server output is shown in black, and user input is in bold.

Notice the difference in the PORT command in this example as opposed to the active FTP example. Here, we see a port being opened on the server (192.168.150.90) system, rather than the client. See the discussion about the format of the PORT command above, in the Active FTP Example section.

testbox1: {/home/p-t/slacker/public_html} % ftp -d testbox2

Connected to testbox2.slacksite.com.

220 testbox2.slacksite.com FTP server ready.

Name (testbox2:slacker): slacker

---> USER slacker

331 Password required for slacker.

Password: TmpPass

---> PASS XXXX

230 User slacker logged in.

---> SYST

215 UNIX Type: L8

Remote system type is UNIX.

Using binary mode to transfer files.

ftp> passive

Passive mode on.

ftp> ls

ftp: setsockopt (ignored): Permission denied

---> PASV

227 Entering Passive Mode (192,168,150,90,195,149).

---> LIST

150 Opening ASCII mode data connection for file list

drwx------ 3 slacker users 104 Jul 27 01:45 public_html

226 Transfer complete.

ftp> quit

---> QUIT

221 Goodbye.

Summary

The following chart should help admins remember how each FTP mode works:

Active FTP :

command : client >1024 -> server 21

data : client >1024 <- server 20

Passive FTP :

command : client >1024 -> server 21

data : client >1024 -> server >1024

A quick summary of the pros and cons of active vs. passive FTP is also in order:

Active FTP is beneficial to the FTP server admin, but detrimental to the client side admin. The FTP server attempts to make connections to random high ports on the client, which would almost certainly be blocked by a firewall on the client side. Passive FTP is beneficial to the client, but detrimental to the FTP server admin. The client will make both connections to the server, but one of them will be to a random high port, which would almost certainly be blocked by a firewall on the server side.

Luckily, there is somewhat of a compromise. Since admins running FTP servers will need to make their servers accessible to the greatest number of clients, they will almost certainly need to support passive FTP. The exposure of high level ports on the server can be minimized by specifying a limited port range for the FTP server to use. Thus, everything except for this range of ports can be firewalled on the server side. While this doesn't eliminate all risk to the server, it decreases it tremendously.

A Beginners Guide to hacking Unix

Note: due to the many different 

Versions of unix (berkley unix, 

Bell system iii, and system v 

The most popular) many commands 

Following may/may not work. I have 

Written them in system v routines. 

Unix/xenix operating systems will 

Be considered identical systems below. 

How to tell if/if not you are on a 

Unix system:  unix systems are quite 

Common systems across the country. 

Their security appears as such: 

Login;     (or login;) 

Password: 

When hacking on a unix system it is 

Best to use lowercase because the unix 

System commands are all done in lower- 

Case. 

Login; is a 1-8 character field. It is 

Usually the name (i.e. Joe or fred) 

Of the user, or initials (i.e. J.jones 

Or f.wilson).  Hints for login names 

Can be found trashing the location of 

The dial-up (use your cn/a to find 

Where the computer is). 

Password: is a 1-8 character password 

Assigned by the sysop or chosen by the 

User. 

      common default logins 

   -------------------------- 

   login;       password: 

   root         root,system,etc.. 

   sys          sys,system 

   daemon       daemon 

   uucp         uucp 

   tty          tty 

   test         test 

   unix         unix 

   bin          bin 

   adm          adm 

   who          who 

   learn        learn 

   uuhost       uuhost 

   nuucp        nuucp 

If you guess a lgin name and you are 

Not asked for a password, and have 

Accessed to the system, then you have 

What is known as a non-gifted account. 

If you guess a correct login and pass- 

Word, then you have a user account. 

And, if you guess the root password, 

Then you have a "super-user" account. 

All unix systems have the following 

Installed to their system: 

Root, sys, bin, daemon, uucp, adm 

Once you are in the system, you will 

Get a prompt. Common prompts are: 

$ 

% 

# 

But can be just about anything the 

Sysop or user wants it to be. 

Things to do when you are in: some 

Of the commands that you may want to 

Try follow below: 

Who is on  (shows who is currently 

            logged on the system.) 

Write name (name is the person you 

            wish to chat with) 

      to exit chat mode try ctrl-d. 

      eot=end of transfer. 

Ls -a      (list all files in current 

            directory.) 

Du -a      (checks amount of memory 

            your files use;disk usage) 

Cd\name    (name is the name of the 

            sub-directory you choose) 

Cd\        (brings your home directory 

            to current use) 

Cat name   (name is a filename either 

            a program or documentation 

            your username has written) 

      most unix programs are written 

      in the c language or pascal 

      since unix is a programmers' 

      environment. 

One of the first things done on the 

System is print up or capture (in a 

Buffer) the file containing all user 

Names and accounts. This can be done 

By doing the following command: 

Cat /etc/passwd 

If you are successful you will a list 

Of all accounts on the system.  It 

Should look like this: 

Root:hvnsdcf:0:0:root dir:/: 

Joe:majdnfd:1:1:joe cool:/bin:/bin/joe 

Hal::1:2:hal smith:/bin:/bin/hal

The "root" line tells the following 

Info : 

Login name=root 

Hvnsdcf   = encrypted password 

0         = user group number 

0         = user number 

Root dir  = name of user 

/         = root directory 

In the joe login, the last part 

"/bin/joe " tells us which directory 

Is his home directory (joe) is. 

In the "hal" example the login name is 

Followed by 2 colons, that means that 

There is no password needed to get in 

Using his name. 

A simple TCP spoofing attack A simple TCP spoofing attack A simple TCP spoofing attack

A simple TCP spoofing attack 

Over the past few years TCP sequence number prediction attacks have become a

real threat against unprotected networks, taking advantage of the inherent

trust relationships present in many network installations.  TCP sequence

number prediction attacks have most commonly been implemented by opening a

series of connections to the target host, and attempting to predict the

sequence number which will be used next.  Many operating systems have

therefore attempted to solve this problem by implementing a method of

generating sequence numbers in unpredictable fashions.  This method does

not solve the problem.

This advisory introduces an alternative method of obtaining the initial

sequence number from some common trusted services.  The attack presented here

does not require the attacker to open multiple connections, or flood a port

on the trusted host to complete the attack.  The only requirement is that

source routed packets can be injected into the target network with fake

source addresses.

This advisory assumes that the reader already has an understanding of how
TCP sequence number prediction attacks are implemented.

The impact of this advisory is greatly diminished due to the large number of
organizations which block source routed packets and packets with addresses
inside of their networks.  Therefore we present the information as more of
a 'heads up' message for the technically inclined, and to re-iterate that
the randomization of TCP sequence numbers is not an effective solution
against this attack.


Technical Details
~~~~~~~~~~~~~~~~~

The problem occurs when particular network daemons accept connections
with source routing enabled, and proceed to disable any source routing
options on the connection.  The connection is allowed to continue, however
the reverse route is no longer used.  An example attack can launched against
the in.rshd daemon, which on most systems will retrieve the socket options
via getsockopt() and then turn off any dangerous options via setsockopt().

An example attack follows.

Host A is the trusted host
Host B is the target host
Host C is the attacker

Host C initiates a source routed connection to in.rshd on host B, pretending
to be host A.

Host C spoofing Host A            -->  Host B in.rshd

Host B receives the initial SYN packet, creates a new PCB (protocol
control block) and associates the route with the PCB.  Host B responds,
using the reverse route, sending back a SYN/ACK with the sequence number.

Host C spoofing Host A  <--         Host B in.rshd

Host C responds, still spoofing host A, acknowledging the sequence number.
Source routing options are not required on this packet.

Host C spoofing Host A            -->  Host B in.rshd

We now have an established connection, the accept() call completes, and
control is now passed to the in.rshd daemon.  The daemon now does IP
options checking and determines that we have initiated a source routed
connection.  The daemon now turns off this option, and any packets sent
thereafter will be sent to the real host A, no longer using the reverse
route which we have specified.  Normally this would be safe, however the
attacking host now knows what the next sequence number will be.  Knowing
this sequence number, we can now send a spoofed packet without the source
routing options enabled, pretending to originate from Host A, and our
command will be executed.

In some conditions the flooding of a port on the real host A is required
if larger ammounts of data are sent, to prevent the real host A from
responding with an RST.  This is not required in most cases when performing
this attack against in.rshd due to the small ammount of data transmitted.

It should be noted that the sequence number is obtained before accept()
has returned and that this cannot be prevented without turning off source
routing in the kernel.

As a side note, we're very lucky that TCP only associates a source route with
a PCB when the initial SYN is received.  If it accepted and changed the ip
options at any point during a connection, more exotic attacks may be possible.
These could include hijacking connections across the internet without playing
a man in the middle attack and being able to bypass IP options checking
imposed by daemons using getsockopt().  Luckily *BSD based TCP/IP stacks will
not do this, however it would be interesting to examine other implementations.

Impact
~~~~~~

The impact of this attack is similar to the more complex TCP sequence
number prediction attack, yet it involves fewer steps, and does not require
us to 'guess' the sequence number.  This allows an attacker to execute
arbitrary commands as root, depending on the configuration of the target
system.  It is required that trust is present here, as an example, the use
of .rhosts or hosts.equiv files.


Solutions
~~~~~~~~~

The ideal solution to this problem is to have any services which rely on
IP based authentication drop the connection completely when initially
detecting that source routed options are present.  Network administrators
and users can take precautions to prevent users outside of their network
from taking advantage of this problem.  The solutions are hopefully already
either implemented or being implemented.

1. Block any source routed connections into your networks
2. Block any packets with internal based address from entering your network.

Network administrators should be aware that these attacks can easily be
launched from behind filtering routers and firewalls.  Internet service
providers and corporations should ensure that internal users cannot launch
the described attacks.  The precautions suggested above should be implemented
to protect internal networks.

Example code to correctly process source routed packets is presented here
as an example.  Please let us know if there are any problems with it.
This code has been tested on BSD based operating systems.

        u_char optbuf[BUFSIZ/3];
        int optsize = sizeof(optbuf), ipproto, i;
        struct protoent *ip;

        if ((ip = getprotobyname("ip")) != NULL)
                ipproto = ip->p_proto;
        else
                ipproto = IPPROTO_IP;
        if (!getsockopt(0, ipproto, IP_OPTIONS, (char *)optbuf, &optsize) &&
            optsize != 0) {
                for (i = 0; i < optsize; ) {
                        u_char c = optbuf[i];
                        if (c == IPOPT_LSRR || c == IPOPT_SSRR)
                                exit(1);
                        if (c == IPOPT_EOL)
                                break;
                        i += (c == IPOPT_NOP) ? 1 : optbuf[i+1];
                }
        }


One critical concern is in the case where TCP wrappers are being used.  If
a user is relying on TCP wrappers, the above fix should be incorporated into
fix_options.c.  The problem being that TCP wrappers itself does not close
the connection, however removes the options via setsockopt().  In this case
when control is passed to in.rshd, it will never see any options present,
and the connection will remain open (even if in.rshd has the above patch
incorporated).  An option to completely drop source routed connections will
hopefully be provided in the next release of TCP wrappers.  The other option
is to undefine KILL_IP_OPTIONS, which appears to be undefined by default.
This passes through IP options and allows the called daemon to handle them
accordingly.


Disabling Source Routing
~~~~~~~~~~~~~~~~~~~~~~~~

We believe the following information to be accurate, however it is not
guaranteed.

--- Cisco

To have the router discard any datagram containing an IP source route option
issue the following command:

no ip source-route

This is a global configuration option.


--- NetBSD

Versions of NetBSD prior to 1.2 did not provide the capability for disabling
source routing.  Other versions ship with source routing ENABLED by default.
We do not know of a way to prevent NetBSD from accepting source routed packets.
NetBSD systems, however, can be configured to prevent the forwarding of packets
when acting as a gateway.

To determine whether forwarding of source routed packets is enabled,
issue the following command:

# sysctl net.inet.ip.forwarding
# sysctl net.inet.ip.forwsrcrt

The response will be either 0 or 1, 0 meaning off, and 1 meaning it is on.

Forwarding of source routed packets can be turned off via:

# sysctl -w net.inet.ip.forwsrcrt=0

Forwarding of all packets in general can turned off via:

# sysctl -w net.inet.ip.forwarding=0


--- BSD/OS

BSDI has made a patch availible for rshd, rlogind, tcpd and nfsd.  This
patch is availible at:

ftp://ftp.bsdi.com/bsdi/patches/patches-2.1

OR via their patches email server

The patch number is
U210-037 (normal version)
D210-037 (domestic version for sites running kerberized version)


BSD/OS 2.1 has source routing disabled by default

Previous versions ship with source routing ENABLED by default.  As far as
we know, BSD/OS cannot be configured to drop source routed packets destined
for itself, however can be configured to prevent the forwarding of such
packets when acting as a gateway.

To determine whether forwarding of source routed packets is enabled,
issue the following command:

# sysctl net.inet.ip.forwarding
# sysctl net.inet.ip.forwsrcrt

The response will be either 0 or 1, 0 meaning off, and 1 meaning it is on.

Forwarding of source routed packets can be turned off via:

# sysctl -w net.inet.ip.forwsrcrt=0

Forwarding of all packets in general can turned off via:

# sysctl -w net.inet.ip.forwarding=0


--- OpenBSD

Ships with source routing turned off by default.  To determine whether source
routing is enabled, the following command can be issued:

# sysctl net.inet.ip.sourceroute

The response will be either 0 or 1, 0 meaning that source routing is off,
and 1 meaning it is on.  If source routing has been turned on, turn off via:

# sysctl -w net.inet.ip.sourceroute=0

This will prevent OpenBSD from forwarding and accepting any source routed
packets.


--- FreeBSD

Ships with source routing turned off by default.  To determine whether source
routing is enabled, the following command can be issued:

# sysctl net.inet.ip.sourceroute

The response will be either 0 or 1, 0 meaning that source routing is off,
and 1 meaning it is on.  If source routing has been turned on, turn off via:

# sysctl -w net.inet.ip.sourceroute=0


--- Linux

Linux by default has source routing disabled in the kernel.


--- Solaris 2.x

Ships with source routing enabled by default.  Solaris 2.5.1 is one of the
few commercial operating systems that does have unpredictable sequence
numbers, which does not help in this attack.

We know of no method to prevent Solaris from accepting source routed
connections, however, Solaris systems acting as gateways can be prevented
from forwarding any source routed packets via the following commands:

# ndd -set /dev/ip ip_forward_src_routed 0

You can prevent forwarding of all packets via:

# ndd -set /dev/ip ip_forwarding 0

These commands can be added to /etc/rc2.d/S69inet to take effect at bootup.


--- SunOS 4.x

We know of no method to prevent SunOS from accepting source routed
connections, however a patch is availible to prevent SunOS systems from
forwarding source routed packets.

This patch is availible at:

ftp://ftp.secnet.com/pub/patches/source-routing-patch.tar.gz

To configure SunOS to prevent forwarding of all packets, the following
command can be issued:

# echo "ip_forwarding/w 0" | adb -k -w /vmunix /dev/mem
# echo "ip_forwarding?w 0" | adb -k -w /vmunix /dev/mem

The first command turns off packet forwarding in /dev/mem, the second in
/vmunix.


--- HP-UX

HP-UX does not appear to have options for configuring an HP-UX system to
prevent accepting or forwarding of source routed packets.  HP-UX has IP
forwarding turned on by default and should be turned off if acting as a
firewall.  To determine whether IP forwarding is currently on, the following
command can be issued:

# adb /hp-ux
ipforwarding?X      <- user input
ipforwarding:
ipforwarding: 1
#

A response of 1 indicates IP forwarding is ON, 0 indicates off.  HP-UX can
be configured to prevent the forwarding of any packets via the following
commands:

# adb -w /hp-ux /dev/kmem
ipforwarding/W 0
ipforwarding?W 0
^D
#

--- AIX

AIX cannot be configured to discard source routed packets destined for itself,
however can be configured to prevent the forwarding of source routed packets.
IP forwarding and forwarding of source routed packets specifically can be
turned off under AIX via the following commands:

To turn off forwarding of all packets:

# /usr/sbin/no -o ipforwarding=0

To turn off forwarding of source routed packets:

# /usr/sbin/no -o nonlocsrcroute=0

Note that these commands should be added to /etc/rc.net



If shutting off source routing is not possible and you are still using
services which rely on IP address authentication, they should be disabled
immediately (in.rshd, in.rlogind).  in.rlogind is safe if .rhosts and
/etc/hosts.equiv are not used.




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