VBS.Beast.C

SUMMARY

This is a encrypted Visual Basic script. If executed, it appends its code to all .vbs files found on the current drive. It creates the file W95inf32.vbs in the WindowsSystem folder. The registry is modified to execute this file when the computer starts. This script does not contain a means by which it can transmit itself.

Protection

• Virus Definitions (Intelligent Updater) March 7, 2001

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: Low
• Modifies Files: Appends its code to all .vbs files on the current drive.

Distribution

• Distribution Level: Low

TECHNICAL DETAILS

When executed, VBS.Beast.B does the following:

1. It appends itself to all .vbs files found on the current drive.
2. It creates the WindowsSystemW95inf32.vbs file.
3. It adds the value
   
   Beast   <path>W95inf32.vbs
   
   to the registry key
   
   HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersionRun
   
   This executes the script when Windows starts.
   
4. If the date is the 13th of the month, the script displays the following message:

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, delete the WindowsSystemW95inf32.vbs file and remove the value "Beast" from the Run key in the registry. Restore overwritten files if needed. Here are the instructions:

To delete the W95inf32.vbs file:

1. Using Windows Explorer, browse to the WindowsSystem folder and locate the W95inf32.vbs file.
2. Select the file, press Delete, and then click Yes to confirm.

To edit the registry:

CAUTION: We strongly recommend that you back up the system registry before making any changes. Incorrect changes to the registry could result in permanent data loss or corrupted files. Please make sure you modify only the keys specified. Please see the document How to back up the Windows registry before proceeding.

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, select the value
   
   Beast  <path>W95inf32.vbs
   
5. Press Delete, and then click Yes to confirm.
6. Close the Registry Editor.

To restore overwritten files (optional):
If .vbs files were overwritten, you can restore them by opening them in a text editor and deleting all of the viral code from the end of the script file.