Where are Trojans hiding in your systems?

Author : Kyle Lai, CISSP, CISA

KLC Consulting, Inc.

klai@klcconsulting.net

www.klcconsulting.net


In any cases of virus/worm/Trojan infections, we should not automatically assume that HKLM\Software\Microsoft\Windows\CurrentVersion\Run registry key is the only place Trojans try to tamper, otherwise we would be in a false sense of security TRAP.

There are many other places on a Windows system that Trojans can add scripts and shortcuts to startup Trojan processes:

[HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run]

[HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunOnce]

[HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunServices]

[HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunServicesOnce]

[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run]

[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\RunOnce]

Note: For the following registry keys, the key value should be exactly "%1 %*" . Any programs that are added to the key value will get executed every time a binary file (.exe, .com) is executed, i.e."Trojan.exe %1 %*".

[HKEY_CLASSES_ROOT\exefile\shell\open\command]

[HKEY_LOCAL_MACHINE\SOFTWARE\Classes\exefile\shell\open\command]

Also, check

Startup folder: to go to this folder, click on Start->Programs->Startup, and right click on Startup and select "Open" from the menu. Check every file in this folder and make sure you know what they are. These files will startup automatically every time you login to your systems.

Windows Scheduler - check if any programs are scheduled to startup at any specific time. Some Trojans use scheduler as a mean for program execution.

For Windows NT, 2000 and XP systems, use AT command to verify. Go to command prompt and type "at" and if there is any scheduled tasks, it will display "Status, ID, Day of execution, Time of execution, and Command line to be executed"

For Windows 9x/ME systems, use Windows Explorer and go to Task Scheduler, which is under My Computer.

Win.ini (load=Trojan.exe or run=Trojan.exe)

system.ini (Shell=Explorer.exe trojan.exe)

autoexec.bat - look for added Trojan files, may be in the following file extensions: .exe, .scr, .pif, .com, .bat

config.sys - look for added Trojan files

Any suspicious or new batch files (.BAT), which might call the actual Trojan.


In addition, watch out for social engineering... Social engineering? Yes. Don't be fooled by processes or programs with similar and/or exactly the same filename as the legitimate Windows system programs. Many known Trojans have included programs with exact same name as Windows system programs, but put them into different folders. Many people lower their guard when they see familiar Windows system programs, and some Trojans did successfully create deceptions and exploit this human vulnerability. If you just use the Windows Task Manager to check processes, you might be fooled if you don't examine them carefully. You might want to use some other tools for detailed examination i.e. pstools from www.systeminternals.com.


Here are some sample filename of files included in recent Trojans: (assuming Windows is installed in c:\windows or c:\winnt)


Explorer.exe - a legitimate program exists in \Windows or \Winnt folder, NOT \Windows\system32 or \Winnt\system32, or anywhere else

Rundll32.exe - a legitimate program exists in \Windows\system32 or \Winnt\system32 folder, not anywhere else

taskmngr.exe - the legitimate program is called "taskmgr.exe", not taskmngr.exe"


Let's be vigilant about the files, registries and different places that Trojan can touch.



Reference:

URL of this article is: http://www.klcconsulting.net/trojan/trojan...ntification.htm

Ocxdll.exe/mIRC Virus Analysis by KLC Consulting: http://www.klcconsulting.net/mirc_virus_analysis.htm

Deloder worm / IRC worm/Trojan Analysis by KLC Consulting: http://www.klcconsulting.net/deloder_virus...us_analysis.htm

The Complete Windows Trojans Paper By Dancho Danchev: http://www.frame4.com/

hi m8 i tried most things u put there and came up with nothing.....ok my prob at the min is i have the PwSteal.trojan .... i have ran virus scan it sees it but cant quarantine it or delete it it says it fixs it but the virus is still there.... when u goto manually remove it u cant coz it asks is it write-protected....

now i have tried running System Works 2003 on live-update still no joy and still i have this virus it is cracking me up at min

plz help me

here is something i posted a long time ago- i don't think trojanforge is up anymore? anyway- this list is pretty much the same as above, but does go over some techniques not explained thusfar...

thanks m8 but to be honest i dont really know much about the registry keys all i know at the min is i cant get the tapiexec.dll file deleted from my computer and i need to get rid of it coz it has the trojan in it plz some simple help would be much gratefull

There is another list of http://www.tlsecurity.com
You can also get from there.

tnx for the information dude

Thanks for the information, really usefull