my box is been hacked,help me!

[Thunderbird]

i used redhat 7.2 linux. yesterday, i found someone use ftp to connect and into my system. i type "netstat -ap" found that a 51501 port was opend ,and it is opend by sshd, i try to modify the sshd_config file ,but i can't find it,i use "locate" to search it,it displayed ,but use "ls" can't display. i use "vi" to modify it ,but no use.it isn't permit.i used root ,and can't modify it.so ,the hacker is very special.please help me!thx

[rac]

Probably the safest thing to do is to immediately disconnect the network connection of the affected machine. The lsof command can help you associate specific processes with open ports; it is likely that a rogue copy of sshd is running on port 51501.
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For every higher wall, there is a taller ladder

[delta407]

[rac]

While I agree with everything that delta407 said, if you have free space of some sort available, it might be useful to keep a copy of the system in its compromised state on spare media, so that you can examine it in more detail at leisure later, with an eye to evaluating how security was broken so that you can take steps to prevent against further attacks in the future.
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For every higher wall, there is a taller ladder

[pjp]

Does anyone know of a 'standard' checklist for where to begin 'evaluating how security was broken'? Just thought I'd ask. Seems relevant.
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Quis separabit? Quo animo?

[Thunderbird]

i know, i tried to copy a new "sshd_config" to instead the rogue copy ,but it is not permitted.i logined by root ,and want to modify the rogue copy,it is not permitted too.how did he do that?

[rac]

[rac]

[dioxmat]

also check out lsattr and chattr .
most rootkits add stealth modules, change binaries and libs, startup scripts, and configuration files.

/me always log everything that happens and keep a statically built system on cd just in case.
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mat

[Thunderbird]

i am not really understand your means, i am a beginner,can you help me to repair the box step by step ? if i can repair the box successfully , i will learn the hack technique too ,and learn more and more knowledge.

[rac]

• Unplug the network connection
  
• Boot from a trusted medium, like the install CD
  
• Mount your compromised filesystems somewhere not in your PATH, like /mnt/something
  
• If you have enough free space available somewhere, make a copy of your entire compromised filesystem using tar or cpio for later analysis - mark it with a big skull and crossbones or something.
  
• In any case, copy all important data files (don't copy any executable programs at this stage, unless you absolutely have to have them, and if you do, make sure you vet them carefully to make sure they have not been modified) somewhere to a backup medium.
  
• Use mkfs to completely wipe the filesystems on the affected disk partitions
  
• Reinstall the system from scratch
  
• Change all passwords
  
• Check each server process running on that machine for security updates and make sure that each is really necessary and configured properly. Look at the machine from the point of view of a remote attacker.

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For every higher wall, there is a taller ladder

[Thunderbird]

thank you for your advice , i will do that . i was very pleasure to be hacked by a special man , because i learned more knowledge from this case.

[delta407]

[Thunderbird]

now, i have found the source of problem, it is SSH trojan. i used the version of 3.4p1 , it is in the list of been trojan below:

OpenSSH version 3.2.2p1, 3.4p1 and 3.4 have been trojaned
Aug, 01 2002 - 17:21
contributed by: hx
OpenSSH Security Advisory (adv.trojan)

1. Systems affected:

OpenSSH version 3.2.2p1, 3.4p1 and 3.4 have been trojaned on the
OpenBSD ftp server and potentially propagated via the normal mirroring
process to other ftp servers. The code was inserted some time between
the 30th and 31th of July. We replaced the trojaned files with their
originals at 7AM MDT, August 1st.

2. Impact:

Anyone who has installed OpenSSH from the OpenBSD ftp server or any
mirror within that time frame should consider his system compromised.
The trojan allows the attacker to gain control of the system as the
user compiling the binary. Arbitrary commands can be executed.

3. Solution:

Verify that you did not build a trojaned version of the sources. The
portable SSH tar balls contain PGP signatures that should be verified
before installation. You can also use the following MD5 checksums for
verification.

MD5 (openssh-3.4p1.tar.gz) = 459c1d0262e939d6432f193c7a4ba8a8
MD5 (openssh-3.4p1.tar.gz.sig) = d5a956263287e7fd261528bb1962f24c
MD5 (openssh-3.4.tgz) = 39659226ff5b0d16d0290b21f67c46f2
MD5 (openssh-3.2.2p1.tar.gz) = 9d3e1e31e8d6cdbfa3036cb183aa4a01
MD5 (openssh-3.2.2p1.tar.gz.sig) = be4f9ed8da1735efd770dc8fa2bb808a

4. Details

When building the OpenSSH binaries, the trojan resides in bf-test.c
and causes code to execute which connects to a specified IP address.
The destination port is normally used by the IRC protocol. A
connection attempt is made once an hour. If the connection is
successful, arbitrary commands may be executed.

Three commands are understood by the backdoor:

Command A: Kill the exploit.
Command D: Execute a command.
Command M: Go to sleep.

5. Notice:

Because of the urgency of this issue, the advisory may not be
complete. Updates will be posted to the OpenSSH web pages if
necessary.


and another question, how can i use the MD5 ?

[dioxmat]

mmm, are you sure this is the openssh troyan ?
emerge does check the md5sum automatically. you can do it by hand with "md5sum".
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mat

[trolley]

[Thunderbird]

[dioxmat]

ooops :)
but then why is this post in gentoo's networking & security uh ? :)
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mat

[Oizoken]

[Thunderbird]

i am so sorry , i will do something by myself.and i really appreciate your help.

[sanity]

You mentioned that Gentoo people know more about Linux? Probably because we have to. Gentoo installation requires more knowledge of Linux and Unix in general than most RedHat desktop users will ever know.

Maybe you should switch to Gentoo, as long as you're installing from scratch. It would be a good exercise in basic Linux concepts.

Plus, I would guess that emerge is harder to trojan than rpm.
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Every time you read a signature, God kills a kitten.

[Xor]

just me 2c

good checklists are available at securityfocus or sans.org...

the command is md5sum

did redhat ever release an rpm of current openssh? last time I checked I could find one... but hey UTSL....

I would suggest something like aide, snort, argus or whatever you like... and oh, iptables wouldn't bat too...

btw - RH is not really a secure Linux distro, if I remember right it is the no 1 Linux distro hacked.

[pjp]

Just in case others don't catch the typo, it is securitYfocus. Thanks for the links.
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Quis separabit? Quo animo?

[Xor]

ok.... after this _-dilema... I guess I deserve it....

a quick guide is available here

the book overview is here (havn't read it) and can be ordered here (I hate linking on amazon, cos they have patented this stupid 1click-feature... )

[rajiv]