Practice



Author: van Hauser / THC
HTML-version by Markus Hübner



I. THE FIRST COMMAND

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. 


$   <- this is a SH prompt

%   <- this is a CSH prompt

If it does not look like the standard prompts above then execute SH. If the prompt stays the same, type "exit" 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).


II. LASTLOG WORKAROUND

 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 : "rlogin " and provide again the password of the hacked account if necessary. After seeing the shell prompt type "exit" to be back again. This will change the header "Last login from ..." etc. to the 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.


III. WHO WORKAROUND

 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 "login" with the same login+password. Type "w" again and if it worked, your origin will be changed to something like "tty05".
Of course you only need to do this if your origin host might attract attention by other users and/or sysadmin.


V. EXECUTING PROGRAMS

Don't execute programs with suspicous names ... ISS and YPX 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 "ps -ef" or "ps -auxwww" and the current command every user is executing with "w" and the most CPU consuming processes with "top" ... so it's really easy to monitor the programs the user(s) are running.


VI. EXECUTING TELNET

 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 NEVER just type "telnet target.host.com". Type "telnet" and then "open target.host.com" 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: USER, LOGNAME, UID, HOME, MAIL - maybe you should do a "cd /tmp" too to change the PWD variable too ... To change those variables: 

      SH : <variable>=<new_value>;export <variable>

           example : USER=nobody;export USER

      CSH: setenv <variable> <new_value>

           example : setenv USER nobody
and don't forget to reset the variables after your telnet if you want to do something with the account before you log out.


VII. REMOVE YOUR FILES

 When you tried exploits - successful or not - delete them immedeantely after trying them - especially if you try them in /tmp ! Nothing is more interesting than snooping in the /tmp 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 ".X11", 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. 


   -->  !  The following 2 points are only possible with root access !  <--

VI. MODIFYING THE LOGS

 The important log files are LASTLOG, WTMP and UTMP. If you were successful in hacking root then you should modify them. They can usually be found in /etc, /var/adm or /var/log ... it differs, just check the man pages.

Which tools should you use? ZAP (or ZAP2) is nice, but it does NOT 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 ZAP : Check the paths defined in the sources for the logs! Try CLOAK2 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 REALLY deletes the entries ... ;)


VII. SYSLOG & LASTCOMM

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 /var/adm or /var/log ... most time it's called "messages" but again can differ - and also check other logfiles there which are generated by auth.* and authpriv.* messages (and of course xferlog etc.). Check the file /etc/syslog.conf to see the correct file and check out what is logged to which file/program/mail/user.

If you see something like "@loghost" 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 ;)
To remove f.e. your hostname from the "messages" logfile execute :
"grep -v evil.host.com messages > /tmp/tmpfile; mv /tmp/tmpfile messages"

LASTCOMM (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 ;-)


VIII. INSTALLING TROJANS

When you install a sniffer, remember that anyone can execute "ifconfig -a" to check if the card is in promiscious mode. Get a rootkit for your unix OS and replace it. Run fixer.c 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 ;)


X. THE END

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 mc@thc.net 

   Remember : Never get lazy. Every work must be done 100% -

              or face the consequences!




Type Bits/KeyID    Date       User ID

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