Backdoor.Sparta

SUMMARY

Backdoor.Sparta is a Trojan horse that allows unauthorized access to the infected computer. This Trojan also attempts to remove several major brands of firewall and antivirus protection, including Norton AntiVirus.

Protection

• Virus Definitions (LiveUpdate™ Weekly) June 26, 2002
• Virus Definitions (Intelligent Updater) June 24, 2002

Threat Assessment

Wild

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

Damage

• Damage Level: Medium
• Compromises Security Settings: Attempts to remove various Firewall and AntiVirus programs

Distribution

• Distribution Level: Low

TECHNICAL DETAILS

Backdoor.Sparta sets up the server for a backdoor access. It connects using sockets. ThisTrojan also attempts to remove several major brands of firewall and antivirus protection, including Norton AntiVirus. After you remove the Trojan, you must reinstall firewall and antivirus programs.

It copies itself as Windows\%System%Rundll32b.exe.

NOTE: %System% is a variable. The worm locates the WindowsSystem folder (by default this is C:WindowsSystem or C:WinntSystem32) and copies itself to that location.

It adds the value

Spfile         Rundll32b.exe

to the registry key

HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersionRun

It also creates the SystemWinstart.bat batch file, which creates the registry entry if it does not exist.

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

Removal depends on whether Norton AntiVirus (NAV) is functioning properly:

• If NAV is functioning properly:
  1. Update the virus definitions, run a full system scan, and delete all files that are detected as Backdoor.Sparta.
  2. Delete the value
     
     Spfile
     
     from the registry key
     
     HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindows
     CurrentVersionRun
     
• If NAV is not functioning properly:
  1. Delete Windows\%System%Rundll32b.exe.
  2. Delete the value
     
     Spfile
     
     from the registry key
     
     HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindows
     CurrentVersionRun
     
  3. Reinstall NAV, update the definitions, and run a full system scan.

For details on how to do this, read the following instructions.

If NAV is functioning properly
To scan with Norton AntiVirus and delete the infected files:

1. Obtain the most recent virus definitions. There are two ways to do this:
   • Run LiveUpdate, which is the easiest way to obtain virus definitions. These virus definitions have undergone full quality assurance testing by Symantec Security Response and are posted to the LiveUpdate servers one time each week (usually Wednesdays) unless there is a major virus outbreak. To determine whether definitions for this threat are available by LiveUpdate, look at the Virus Definitions (LiveUpdate) line at the top of this write-up.
   • Download the definitions using the Intelligent Updater. Intelligent Updater virus definitions have undergone full quality assurance testing by Symantec Security Response. They are posted on U.S. business days (Monday through Friday). They must be downloaded from the Symantec Security Response Web site and installed manually. To determine whether definitions for this threat are available by the Intelligent Updater, look at the Virus Definitions (Intelligent Updater) line at the top of this write-up.
     
     Intelligent Updater virus definitions are available here. For detailed instructions on how to download and install the Intelligent Updater virus definitions from the Symantec Security Response Web site, click here.
     
2. Start Norton AntiVirus (NAV), and make sure that NAV is configured to scan all files.
   • NAV Consumer products: Read the document How to configure Norton AntiVirus to scan all files.
   • NAV Enterprise products: Read the document How to verify a Symantec Corporate antivirus product is set to scan All Files.
3. Run a full system scan.
4. Delete all files that NAV detects as Backdoor.Sparta.

To remove the value from the registry:

CAUTION: Symantec strongly recommends that you back up the registry before you make any changes to it. Incorrect changes to the registry can result in permanent data loss or corrupted files. Modify only the keys that are specified. Read the document How to make a backup of the Windows registry for instructions.

1. Click Start, and click Run. The Run dialog box appears.
2. Type regedit and then click OK. The Registry Editor opens.
3. Navigate to the following key:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun
   
4. In the right pane, delete the following value:
   
   Spfile
   
5. Click Registry, and click Exit.

If NAV is not functioning properly
If NAV does not start or you cannot run a scan or LiveUpdate, follow these instructions.

To delete the file Windows\%System%Rundll32b.exe file:
Follow the instructions for your version of Windows.

• Windows 95/98/Me/NT/2000
1. Click Start, point to Find or Search, and then click Files or Folders.
2. Make sure that "Look in" is set to (C:) and that "Include subfolders" is checked.
3. In the "Named" or "Search for..." box, type--or copy and paste--the following file name:
   
   RUNDLL32B.EXE
   
4. Click Find Now or Search Now.
5. Delete the Rundll32b.exe files that result from the search.
• Windows XP
1. Click Start, and then click Search.
2. Click All files and folders.
3. In the "All or part of the file name" box, type--or copy and paste--the following file name:
   
   RUNDLL32B.EXE
   
4. Verify that "Look in" is set to "Local Hard Drives" or to (C:).
5. Click "More advanced options."
6. Check "Search system folders."
7. Check "Search subfolders."
8. Click Search.
9. Delete the Rundll32b.exe files that result from the search.

To remove the value from the registry:

CAUTION: Symantec strongly recommends that you back up the registry before you make any changes to it. Incorrect changes to the registry can result in permanent data loss or corrupted files. Modify only the keys that are specified. Read the document How to make a backup of the Windows registry for instructions.

1. Click Start, and click Run. The Run dialog box appears.
2. Type regedit and then click OK. The Registry Editor opens.
3. Navigate to the following key:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun
   
4. In the right pane, delete the following value:
   
   Spfile
   
5. Click Registry, and click Exit.

To reinstall NAV:

1. Close all programs, and restart the computer.
2. Reinstall NAV from your original installation CD or downloaded installation files.
3. Start Norton AntiVirus (NAV), and make sure that NAV is configured to scan all files.
   • NAV Consumer products: Read the document How to configure Norton AntiVirus to scan all files.
   • NAV Enterprise products: Read the document How to verify a Symantec Corporate antivirus product is set to scan All Files.
4. Run a full system scan.
5. Delete all files that NAV detects as Backdoor.Sparta.