BAT.Disom.Worm

SUMMARY

BAT.Disom.Worm is a worm that spreads through file-sharing networks and through IRC. It has a destructive payload that attempts to delete numerous files, including those belonging to some antivirus programs.

Protection

• Virus Definitions (LiveUpdate™ Weekly) September 3, 2003
• Virus Definitions (Intelligent Updater) September 2, 2003

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: Medium
• Deletes Files: Taskman.exe. Deletes .dll, .reg, .log, .dat, .txt, .ini, .def, .exe, .hlp, .cnt from various antivirus program folders.

Distribution

• Distribution Level: Medium
• Shared Drives: Attempts to spread through the KaZaA file-sharing network.

TECHNICAL DETAILS

When BAT.Disom.Worm is executed, it does the following:

1. Disables the mouse and keyboard.
   
   
2. Copies itself as:
   • %Windir%Cxv9.bat
   • %Windir%System32Cxv9.bat
     
     
3. Deletes the registry key:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun
   
   
4. Deletes the Windows file, Taskman.exe.
   
   
5. Deletes files that have these extensions:
   
   .exe
   .dll
   .hlp
   .dat
   .ini
   .idx
   .log
   
   from these folders:
   
   C:Progra~1Norton~1
   C:Progra~1Mcafee
   
   
6. Deletes the files that have these extensions:
   
   .dll
   .reg
   .log
   .dat
   .txt
   .ini
   .def
   .exe
   .hlp
   .cnt
   
   from the C:Progra~1Norton~1Norton~1 folder.
   
   
7. Modifies the %Mirc%Script.ini and %Pirch98%Events.ini files so that it spreads through these file-sharing programs.
   
   
8. Infects all the .bat and .con files in the %Windir% folder.
   
   
9. Copies itself as these files:
   • %Kazaa Shared Folder%porn.jpg.bat
   • %Kazaa Shared Folder%sex.jpg.bat
   • %Kazaa Shared Folder%love.jpg.bat
   • %Kazaa Shared Folder%hotmail-hack.exe.bat
   • %Kazaa Shared Folder%microsoft-keygen.exe.bat
   • %Kazaa Shared Folder%ea-games_keygen.exe.bat
     
     
10. Deletes numerous files from the following folders:
    • C:Inetpub
    • C:Progra~1Intern~1
    • C:Progra~1Messen~1
    • C:InetpubWwwroot
    • C:Progra~1Symant~1
    • C:Progra~1Symant~1Liveup~1
      
      
11. Shuts down the computer.

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.

NOTE: If BAT.Disom.Worm has already run, you may not be able to run LiveUpdate or start your antivirus software as directed in the following instructions. In this case, re-install the product first.

1. Disable System Restore (Windows Me/XP).
2. Update the virus definitions.
3. Run a full system scan and delete all the files detected as BAT.Disom.Worm.
4. Restore the Taskman.exe file if it was deleted.

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

1. Disabling 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"

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. Updating 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 on U.S. business days (Monday through Friday). 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.

3. Scanning for and deleting 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 BAT.Disom.Worm, click Delete.

4. Restoring the Taskman.exe file
Taskman.exe is the Windows Task Manager. Windows and some programs use it to schedule various events, such as Automatic LiveUpdate. If you use any programs that use this file, you should replace it from a clean backup or re-install it. Read your Windows documentation for information on how to do this.