Trojan.KillAV.F

SUMMARY

Trojan.KillAV.F is a Trojan horse that installs a Browser Helper Object(BHO) and disables security software. This BHO causes the browser to download a variant of Infostealer.Bankash.

Protection

• Virus Definitions (LiveUpdate™ Weekly) March 30, 2005
• Virus Definitions (Intelligent Updater) March 28, 2005

Threat Assessment

Wild

• Wild Level: Low
• Number of Infections: 0 - 49
• Number of Sites: 0 - 2
• Geographical Distribution: Low
• Threat Containment: Easy
• Removal: Moderate

Damage

• Damage Level: Low
• Payload: Installs a Browser Helper Object that downloads dialers and other threats.
• Compromises Security Settings: Disables security software

Distribution

• Distribution Level: Low

TECHNICAL DETAILS

When Trojan.KillAV.F runs, it performs the following actions:

1. Adds the following GUID:
   
   {DE23A040-D6AA-43ca-9B86-D9BE3DAA6FE7}
   
   to any of the following registry subkeys:
   
   HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersionExplorerBrowser Helper Objects
   HKEY_CLASSES_ROOTCLSID
   HKEY_LOCAL_MACHINESoftwareClassesCLSID
   
   to install a Browser Helper Object.
   
   
2. Copies itself to %Windir%strto.exe
   
   Note: %Windir% is a variable that refers to the Windows installation folder. By default, this is C:Windows or C:Winnt.
   
   
3. Adds the file %System%ash.dll
   
   Note: %System% is a variable that refers to the System folder. By default this is C:WindowsSystem (Windows 95/98/Me), C:WinntSystem32 (Windows NT/2000), or C:WindowsSystem32 (Windows XP).
   
   
4. Downloads a file and saves it as %System%javafix4.dll
   
   
5. Adds some of the following registry subkeys:
   
   HKEY_LOCAL_MACHINESoftwareClassesAntispy.Antispy
   HKEY_LOCAL_MACHINESoftwareClassesAntispy.Antispy.1
   HKEY_LOCAL_MACHINESoftwareClassesApplicationsmplayer2.exe
   HKEY_LOCAL_MACHINESoftwareClassesApplicationsmspaint.exe
   HKEY_LOCAL_MACHINESoftwareClassesApplicationsNavw32.exe
   
   
6. Adds the values:
   
   "Install_em" = "ok"
   "Install_pw" = "ok"
   
   to the registry key:
   
   HKEY_CURRENT_USERSoftwareMicrosoftWindowsCurrentVersion
   
   
7. Attempts to terminate the following processes at 1 minute intervals:
   
   
   • NMAIN.EXE
   • SYMLCSVC.EXE
   • NAVAPSVC.EXE
   • CCSETMGR.EXE
   • SAVSCAN.EXE
   • CCEVTMGR.EXE
   • CCAPP.EXE
   • MCSHIELD.EXE
   • GIANTANTISPYWAREUPDATER
   • AVCONSOL.EXE
   • GIANTANTISPYWAREMAIN
   • VSMAIN.EXE
   • GCIPTOHOSTQUEUE
   • VSHWIN32.EXE
   • GCASSWUPDATER
   • AVSYNMGR.EXE
   • GCASSERVALERT
   • QCLEAN.EXE
   • KAVSVC.EXE
   • KAVSEND.EXE
   • KAV.EXE
   • GCASSERV
   • GCASNOTICE
   • RULAUNCH.EXE
   • VSSTAT.EXE
   • GCASINSTALLHELPER
   • ALOGSERV.EXE
   • GCASDTSERV
   • GCASCLEANER
     
     
8. Searches the compromised computer for the following files and deletes any that it finds:
   
   
   • C:Program FilesNorton Antivirus*.*
   • C:Program FilesCommon FilesNetwork Associates*.*
   • C:Program FilesMcAfee*.*
   • C:Program FilesKaspersky Lab*.*
   • C:Program FilesMicrosoft AntiSpyware*.*
     
     
9. Deletes the startup registry entry for any antivirus programs that are installed on the infected computer, so the programs will no longer automatically run when Windows starts.
   
   Note: The startup entry is usually located in one of the following registry subkeys:
   
   HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersionRun
   HKEY_CURRENT_USERSoftwareMicrosoftWindowsCurrentVersionRun
   
   
10. May attempt to download and run a variant of Infostealer.Bankash from 195.225.177.35/askt.exe

Recommendations

Symantec Security Response encourages all users and administrators to adhere to the following basic security "best practices":

• Turn off and remove unneeded services. By default, many operating systems install auxiliary services that are not critical, such as an FTP server, telnet, and a Web server. These services are avenues of attack. If they are removed, blended threats have less avenues of attack and you have fewer services to maintain through patch updates.
• If a blended threat exploits one or more network services, disable, or block access to, those services until a patch is applied.
• Always keep your patch levels up-to-date, especially on computers that host public services and are accessible through the firewall, such as HTTP, FTP, mail, and DNS services (for example, all Windows-based computers should have the current Service Pack installed.). Additionally, please apply any security updates that are mentioned in this writeup, in trusted Security Bulletins, or on vendor Web sites.
• Enforce a password policy. Complex passwords make it difficult to crack password files on compromised computers. This helps to prevent or limit damage when a computer is compromised.
• Configure your email server to block or remove email that contains file attachments that are commonly used to spread viruses, such as .vbs, .bat, .exe, .pif and .scr files.
• Isolate infected computers quickly to prevent further compromising your organization. Perform a forensic analysis and restore the computers using trusted media.
• Train employees not to open attachments unless they are expecting them. Also, do not execute software that is downloaded from the Internet unless it has been scanned for viruses. Simply visiting a compromised Web site can cause infection if certain browser vulnerabilities are not patched.

REMOVAL

The following instructions pertain to all current and recent Symantec antivirus products, including the Symantec AntiVirus and Norton AntiVirus product lines.

1. Disable System Restore (Windows Me/XP).
2. Reinstall the Symantec antivirus program.
3. Update the virus definitions.
4. Run a full system scan and delete all the files detected as Trojan.KillAV.F.
5. Delete any values added to the registry.
   

For specific details on each of these steps, read the following instructions.

1. To disable System Restore (Windows Me/XP)
If you are running Windows Me or Windows XP, we recommend that you temporarily turn off System Restore. Windows Me/XP uses this feature, which is enabled by default, to restore the files on your computer in case they become damaged. If a virus, worm, or Trojan infects a computer, System Restore may back up the virus, worm, or Trojan on the computer.

Windows prevents outside programs, including antivirus programs, from modifying System Restore. Therefore, antivirus programs or tools cannot remove threats in the System Restore folder. As a result, System Restore has the potential of restoring an infected file on your computer, even after you have cleaned the infected files from all the other locations.

Also, a virus scan may detect a threat in the System Restore folder even though you have removed the threat.

For instructions on how to turn off System Restore, read your Windows documentation, or one of the following articles:

• How to disable or enable Windows Me System Restore
• How to turn off or turn on Windows XP System Restore

Note: When you are completely finished with the removal procedure and are satisfied that the threat has been removed, re-enable System Restore by following the instructions in the aforementioned documents.

For additional information, and an alternative to disabling Windows Me System Restore, see the Microsoft Knowledge Base article: Antivirus Tools Cannot Clean Infected Files in the _Restore Folder, Article ID: Q263455.


2. To reinstall the Symantec antivirus program
As this virus attempts to remove the files and registry subkeys that your Symantec antivirus program uses, you may need to reinstall the program. If your Symantec antivirus program is not working properly, uninstall, and then reinstall it.

3. To update the virus definitions
Symantec Security Response fully tests all the virus definitions for quality assurance before they are posted to our servers. There are two ways to obtain the most recent virus definitions:

• Running LiveUpdate, which is the easiest way to obtain virus definitions: These virus definitions are posted to the LiveUpdate servers once each week (usually on Wednesdays), unless there is a major virus outbreak. To determine whether definitions for this threat are available by LiveUpdate, refer to the Virus Definitions (LiveUpdate).
• Downloading the definitions using the Intelligent Updater: The Intelligent Updater virus definitions are posted daily. You should download the definitions from the Symantec Security Response Web site and manually install them. To determine whether definitions for this threat are available by the Intelligent Updater, refer to the Virus Definitions (Intelligent Updater).
  
  The Intelligent Updater virus definitions are available: Read: How to update virus definition files using the Intelligent Updater for detailed instructions.

4. To scan for and delete the infected files

1. Start your Symantec antivirus program and make sure that it is configured to scan all the files.
   • For Norton AntiVirus consumer products: Read the document: How to configure Norton AntiVirus to scan all files.
   • For Symantec AntiVirus Enterprise products: Read the document: How to verify that a Symantec Corporate antivirus product is set to scan all files.
2. Run a full system scan.
3. If any files are detected as infected with Trojan.KillAV.F, click Delete.
   
   Note: If your Symantec antivirus product reports that it cannot delete an infected file, Windows may be using the file. To fix this, run the scan in Safe mode. For instructions, read the document: How to start the computer in Safe Mode. Once you have restarted in Safe mode, run the scan again.
   
   After the files are deleted, restart the computer in Normal mode and proceed with section 4.
   

5. To delete the value from the registry
Important: Symantec strongly recommends that you back up the registry before making any changes to it. Incorrect changes to the registry can result in permanent data loss or corrupted files. Modify the specified subkeys only. Read the document: How to make a backup of the Windows registry, for instructions.

1. Click Start > Run.
2. Type regedit
   
   Then click OK
   
   
3. Navigate to and delete the subkeys:
   
   HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersionExplorerBrowser Helper Objects{DE23A040-D6AA-43ca-9B86-D9BE3DAA6FE7}
   HKEY_CLASSES_ROOTCLSID{DE23A040-D6AA-43ca-9B86-D9BE3DAA6FE7}
   HKEY_LOCAL_MACHINESoftwareClassesCLSID{DE23A040-D6AA-43ca-9B86-D9BE3DAA6FE7}
   
   
4. Exit the Registry Editor.