Interesting text explaining how to cover your tracks when you leave the system.
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<TITLE>How to cover your tracks - Practice</TITLE>
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<h2>Practice</h2><br>
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<tr><td>Author: <I><a href="mailto:mc@thc.net">van Hauser</a> / THC</I><br>
HTML-version by <a href="mailto:matic@bau2.uibk.ac.at"><I>Markus Hübner</I></a>
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<br>
<!PART TWO : PRACTICE>
<br>
<FONT SIZE=1 COLOR="000080"><H2>I. THE FIRST COMMAND</H2></FONT>
The first command you should enter after logging in with a hacked account
is a shell different from the one you are currently running as login shell.
The purpose is to disable history saving of the commands you'll type in
while hacking. A history check by the real user or sysadmin reveils your
presence and what you did!!
If you are running a CSH then execute a SH and vice versa.
<P></P>
<pre>
$ <- this is a SH prompt
% <- this is a CSH prompt
</pre>
<P></P>
If it does not look like the standard prompts above then execute SH.
If the prompt stays the same, type "<TT>exit</TT>" and execute the CSH ...
The reason for using these two shells and not bash, ksh, zsh etc. is
that these two are simple with no extra options enabled by default
(like history saving).
<P></P>
<br>
<FONT SIZE=1 COLOR="000080"><H2>II. LASTLOG WORKAROUND</H2></FONT>
If you saw a text like "Last successful login from alpha.master.mil"
when you logged on with the hacked account and you can't hack root or
don't want to disrupt the system logs with deleting data then execute
the following : "<TT>rlogin <the_host_you_are_on></TT>" and provide again the
password of the hacked account if necessary. After seeing the shell
prompt type "<TT>exit</TT>" to be back again. This will change the header
"Last login from ..." etc. to the <current host> or "localhost"
which is much more unsuspicious than "site.real.user.never.saw.com"
Of course you only need to do this if your origin host might attract
attention to user and/or sysadmin.
<P></P>
<br>
<FONT SIZE=1 COLOR="000080"><H2>III. WHO WORKAROUND</H2></FONT>
After completing step 1 + 2 type "w" ... you'll see all currently
online users ... with the adress they logged on from. Once again
something like your origin host in the netherlands will be very
suspicious to users and/or root if the site is in the usa.
If you can't hack root or once again don't want to tamper with the
log files you can try a bug which works still for many up2date
unix distributions: just execute "<TT>login</TT>" with the same login+password.
Type "<TT>w</TT>" again and if it worked, your origin will be changed to
something like "tty05".<BR>
Of course you only need to do this if your origin host might attract
attention by other users and/or sysadmin.
<p>
<br>
<FONT SIZE=1 COLOR="000080"><H2>V. EXECUTING PROGRAMS</H2></FONT>
Don't execute programs with suspicous names ... <TT>ISS</TT> and <TT>YPX</TT> are for
example very suspicous, and a skilled admin knows what's going on if
he sees a user running "loadmodule SandraBullok" on his Sun ... ;-)
Either you copy & rename the commands or you use those sources around
which exchanges the command name in the process list.
Btw. the process list can be checked by "<TT>ps -ef</TT>" or "<TT>ps -auxwww</TT>" and
the current command every user is executing with "<TT>w</TT>" and the most CPU
consuming processes with "<TT>top</TT>" ... so it's really easy to monitor
the programs the user(s) are running.
<P></P>
<br>
<FONT SIZE=1 COLOR="000080"><H2>VI. EXECUTING TELNET</H2></FONT>
There are only two things which should be said about about using telnet
for hacking purpose (e.g. doing a telnet to the next target).
First <I>NEVER</I> just type "<TT>telnet target.host.com</TT>". Type "<TT>telnet</TT>" and then
"<TT>open target.host.com</TT>" which will not show up as parameter in the process
list. The seconds is that some telnet clients do export enviroment
variables. And if your hack is detected and they could trace the
connection back to your origin host they could also have got the account
you used on the origin host. So redefine (to anything you want) the
following environement variables before starting telnet, rlogin or similar:
<TT>USER</TT>, <TT>LOGNAME</TT>, <TT>UID</TT>, <TT>HOME</TT>, <TT>MAIL</TT> - maybe you should do a "<TT>cd /tmp</TT>" too
to change the <TT>PWD</TT> variable too ...
To change those variables:
<pre>
SH : <variable>=<new_value>;export <variable>
<I>example</I> : USER=nobody;export USER
CSH: setenv <variable> <new_value>
<I>example</I> : setenv USER nobody
</pre>
and don't forget to reset the variables after your telnet if you want to
do something with the account before you log out.
<P></P>
<br>
<FONT SIZE=1 COLOR="000080"><H2>VII. REMOVE YOUR FILES</H2></FONT>
When you tried exploits - successful or not - delete them immedeantely
after trying them - especially if you try them in <TT>/tmp</TT> !
Nothing is more interesting than snooping in the <TT>/tmp</TT> directory to see
what other users are doing ... If you really need to work in the temp
directory (because suid is squashed in your home dir) then create a
usual directory like "<TT>.X11</TT>", and give it 711 permissions.
Remember, if someone snoops in the directories while you are hacking or
your loose connection and can't relogin or you forget about them you
are in deep trouble.
<P></P>
<pre>
--> ! The following 2 points are only possible with root access ! <--
</pre>
<br>
<FONT SIZE=1 COLOR="000080"><H2>VI. MODIFYING THE LOGS</H2></FONT>
The important log files are <B>LASTLOG</B>, <B>WTMP</B> and <B>UTMP</B>.
If you were successful in hacking root then you should modify them.
They can usually be found in <TT>/etc</TT>, <TT>/var/adm</TT> or <TT>/var/log</TT> ... it differs,
just check the man pages.<P></P>
Which tools should you use? <TT>ZAP</TT> (or <TT>ZAP</TT>2) is nice, but it does <i>NOT</i> delete
you from the logs but overwrite the entries with zeros. CERT already
published tools which easily check the logs for those overwritten entries.
And nothing shouts more "Hey there's a hacker on the system with root
access!" into the sysadmin's face than that.
Important for <TT>ZAP</TT> : Check the paths defined in the sources for the logs!
Try <TT>CLOAK2</TT> which can change the data of the important data fields ;) But
it doesn't compile on all unix OS types.
You can also try CLEAR, included in this magazine, which <i>REALLY</i> deletes
the entries ... ;)
<p>
<br>
<FONT SIZE=1 COLOR="000080"><H2>VII. SYSLOG & LASTCOMM</H2></FONT>
You should also check the syslog messages logfile if maybe entries with
your hacked account or your origin host are in it. It's usually located
in <TT>/var/adm</TT> or <TT>/var/log</TT> ... most time it's called "messages" but again
can differ - and also check other logfiles there which are generated by
<TT>auth.*</TT> and <TT>authpriv.*</TT> messages (and of course <TT>xferlog</TT> etc.).
Check the file <TT>/etc/syslog.conf</TT> to see the correct file and check out what
is logged to which file/program/mail/user.<P></P>
If you see something like "<TT>@loghost</TT>" and you find your origin host in
the messages file than you've got a problem. It's also logged at another
site which is most time not accessible from remote. But try to install
a sniffer, (see section VIII. !) and check if a root does a successful
login to the loghost - and then you've got also the password for that
host and are in to handle the problem ;)<BR>
To remove f.e. your hostname from the "messages" logfile execute :<BR>
"<TT>grep -v evil.host.com messages > /tmp/tmpfile; mv /tmp/tmpfile messages</TT>"
<P></P>
<TT>LASTCOMM</TT> (from accton etc.) is a tool to log all executed commands, with
a flag if the file executed had the SUID flag set and if a command was
executed by root. You can find this logfile in the same directory as the
syslog file. That's a really evil tool against hackers but - luck! -
most times it is not installed. But now you don't have to fear that
anymore :) Get Zhart's excellent ACCT Cleaner and feel the freedom ;-)
<p>
<br>
<FONT SIZE=1 COLOR="000080"><H2>VIII. INSTALLING TROJANS</H2></FONT>
When you install a sniffer, remember that anyone can execute "<TT>ifconfig -a</TT>"
to check if the card is in promiscious mode. Get a rootkit for your unix
OS and replace it. Run <TT>fixer.c</TT> on it for the correct checksum and date/time
but check the root account first if maybe tripwire or other binary checker
are installed! Remember this for every binary you replace. If the binary
is in a directory which is NFS mounted and can't be remounted in write mode
then you must first hack the NFS host - life isn't easy sometimes ;)
<p>
<br>
<FONT SIZE=1 COLOR="000080"><H2>X. THE END</H2></FONT>
I hope you had fun and learned alot from these two textfiles, the
theory/background and the practice one.
For updates, tips, tricks etc. just email me at <a href="mailto:mc@thc.net">mc@thc.net</a>
<pre>
Remember : Never get lazy. Every work must be done 100% -
or face the consequences!
</pre>
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<pre>
Type Bits/KeyID Date User ID
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</pre>
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