Re: odd proftpd activity

From: Bit Twister (BitTwister@localhost.localdomain)
Date: 04/19/02


From: BitTwister@localhost.localdomain (Bit Twister)
Date: Thu, 18 Apr 2002 23:16:00 GMT

On Thu, 18 Apr 2002 10:20:24 +0200 (CEST), Nomen Nescio wrote:
>
> Hi, I just noticed a proftpd.log file, never used proftpd before
> and I dont understand why it's suddenly being used or what is
> starting it up. Is this something I should be concerned about
> only I dont know what it's up to?

If you and/or your roommate did not use ftp, you have been cracked.
The fact that they did not cover their tracks indicates it was
a script kiddie running a cracking sweet and got into your box
and did know enough to clean up afterwards.

First, Unplug your system from the internet, Your machine is a menace to
society and you until it's cleaned it up.

Here is why you need a FORMAT and clean install when your box IS cracked.
   http://www.linuxdoc.org/LDP/LG/issue36/kuethe.html
4'th paragraph.

Think about that paragraph.
You cannot use ANY of your pc's utilities to see if your box is cracked
and find what addtional files are installed.

http://www.chkrootkit.org has a program for checking for rootkit installs
on the cracked box. That will tell you about known root kits if you have one.
The cracker may not have installed a rootkit.

What you can do is have a dual boot system. You install a second copy of
your OS and label it Auditor. You never, EVER mount it from the internet OS.

Anytime you THINK you've been cracked, you can boot into Auditor, mount the
internet os partition and start checking the internet OS partitions for new
files and whatnot.

Any time you KNOW your're box is cracked, you should:
o Pull the box off the network. You do not want the police taking
        you and your equipment to jail because a cracker used it
        to crack a bank or military site. If the cracker removes their
        backtracks to their box, you get to do the jail time.

o Put the hardrive(s) into a standalone machine,
        mount the disk(s) readonly,
        save any data, user files, ...,

o Save a full copy of the disk(s) for your forensic attempt,
        save the disk(s) for FBI forensics if it's a Big, BIG dollar loss.

o Re-FORMAT disk drives and do a fresh install from known clean
        source to remove any possible back doors and/or password sniffers
        the cracker installed.

o Restore your saved files, verify that the restored files
        do not have the suid bit set "find / -perm +6000 -ls".

o Have everyone on the box's network change passwords and
        tell them that the cracker may have been running a
        password sniffer so they will not use the passwords ever again.
        Any other boxes logged into from the cracked box should
        have their passwords changed.

Install a modern firewall. Example: iptables is better than ipchains.
If you have a spare linux computer, you can use it to port scan
your box with nmap from http://www.insecure.org/nmap/

Get all the vendor updates to your distro.

You might want to read Armoring Linux
        http://www.linuxdoc.org/HOWTO/Security-Quickstart-HOWTO/index.html
        http://www.enteract.com/~lspitz/linux.html
        http://www.linuxsecurity.com/docs/colsfaq.html
        http://www.securityportal.com/lskb/articles/
        http://www.securityportal.com/lasg/
keep an eye on
        http://www.cert.org/advisories/

For cheap install cd's
http://cart.cheapbytes.com/cgi-bin/cart
top left under Products.
For people accross the pond,
        http://www.linuxemporium.co.uk
        http://www.linux123.co.uk/

Never login as root unless you have to.
Always login from the console, no su, telnet, ssh,..
That way a keystroke logger in your user account cannot
catch your root login password.

You can audit your system if you are using the rpm package manager with
  rpm -Va | grep '..5' > /tmp/verify.log
Runs for a while; more than 5 minutes.

/tmp/verify.log will contain changes which you have made using
configuration tools

Hope crackers do not put in a rootkit which makes the rpm check obsolete.
I think this has happened, though not sure. On one of my boxes
it cored after about 2 minutes, log looked like it ran but never completes
the audit.

rpm -Va | grep '..5' will give you a warm feeling about what changed.
That warm feeling might turn into the warm feeling you get when
you do not get to the bathroom in time. :(

The cracker could install trojaned files some where else and modify
PATH to use them instead of the files you just checked.
You could look at the report and see
        S.5....T c /root/.bash_profile
        S.5....T c /root/.bashrc
You see that and say, "Ok, I did change those. No problem."
BZZZZzzit. WRONG answer, Cracker changed your PATH and you are
running his code.

It also dose not show additional files. I have created a site file in
/etc/profile.d which puts my site/bin into PATH.

Cracker can add his own cracked.sh file to change/add to PATH and
create aliases to substitute a stock command for his code.



Relevant Pages

  • Re: I think I have been hacked
    ... > I have a RH 6.2 Linux server which provides internet ... > connection for my home network of several Win9x PC's and one RH72 ... Here is why you need a FORMAT and clean install when your box IS cracked. ... The cracker may not have installed a rootkit. ...
    (comp.os.linux.security)
  • Re: I think I have been hacked
    ... > I have a RH 6.2 Linux server which provides internet ... > connection for my home network of several Win9x PC's and one RH72 ... Here is why you need a FORMAT and clean install when your box IS cracked. ... The cracker may not have installed a rootkit. ...
    (comp.os.linux.security)
  • Re: cannot replace binaries after being rootkitted
    ... Here is why you need a FORMAT and clean install when your box IS cracked. ... The cracker may not have installed a rootkit. ... EVER mount it from the internet OS. ...
    (comp.os.linux.security)
  • Re: How was my Firewall HACKED???
    ... Here is why you need a FORMAT and clean install when your box IS cracked. ... The cracker may not have installed a rootkit. ... EVER mount it from the internet OS. ... Always login from the console, no su, telnet, ssh,.. ...
    (comp.os.linux.security)
  • Re: How was my Firewall HACKED???
    ... Here is why you need a FORMAT and clean install when your box IS cracked. ... The cracker may not have installed a rootkit. ... EVER mount it from the internet OS. ... Always login from the console, no su, telnet, ssh,.. ...
    (comp.os.linux.security)