W32.HLLP.Gosusub

SUMMARY

W32.HLLP.Gosusub is a virus that infects most executable files on all local drives and mapped network drives. It deletes all .txt files that it finds. This virus contains bugs that may cause it to corrupt executable files when it infects them.

Protection

• Virus Definitions (Intelligent Updater) January 30, 2002

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
• Payload Trigger: During infection
• Payload: Delete all files with the extension .TXT

Distribution

• Distribution Level: Low

TECHNICAL DETAILS

W32.HLLP.Gosusub is a prepending virus that was written in a high-level language (HLL), such as C++; thus, the HLLP name.

When it is executed, the virus performs the following actions:

It creates the file C:WindowsWin386.exe.

It then adds the value

win386     C:WINDOWSwin386.exe

to the registry key

HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun

This virus also modifies the System.ini file to contain the following line:

shell=explorer.exe win386.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

To remove this virus, repair files that are detected as W32.HLLP.Gosusub, remove the value that the virus added to the registry, and remove the text that it added to the System.ini file.

To remove the virus:

1. Run LiveUpdate to make sure that you have the most recent virus definitions.
2. Start Norton AntiVirus (NAV), and make sure that NAV is configured to scan all files. For instructions on how to do this, read the document How to configure Norton AntiVirus to scan all files.
3. Run a full system scan.
4. If any files are detected as infected by W32.HLLP.Gosusub, click Repair. Files that cannot be repaired, or that no longer function after you try to repair them, should be replaced from a clean backup or reinstalled.

To edit the registry:

CAUTION: We strongly recommend 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 back up 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:
   
   win386     C:WINDOWSwin386.exe
   
5. Click Registry, and then click Exit

To edit the System.ini file:
Follow these steps only if you are running Windows 95/98/Me.

1. Click Start, and click Run.
2. Type the following, and then click OK:
   
   edit c:windowssystem.ini
   
   The MS-DOS Editor opens.
   
   NOTE: If Windows is installed in a different location, make the appropriate path substitution.
   
3. Locate the line that begins with shell=explorer.exe
4. Position the cursor immediately to the right of the ".exe" in "explorer.exe"
5. Delete the text win386.exe
   
   The line should now look like:
   
   shell=explorer.exe
   
   NOTE: Some computers may have an entry other than Explorer.exe after shell=. If this is the case and you are running an alternative Windows shell, then change this line to shell=explorer.exe for now. You can change it back to your preferred shell after you have finished this procedure.
   
6. Click File, click Exit, and then click Yes when you are prompted to save the changes.