VBS.Breberka.B@mm

SUMMARY

VBS.Breberka.B@mm is an variant of the VBS.Breberka.A@mm worm. It sends itself as an attachment to all contacts in all MAPI address books. The message is:

Subject: Anti-Virus Warning!!!
Message: r u safe? [Y/N] ;)))
Attachment: Sircamremover.txt <10 blank spaces> .vbe

The worm also attempts to connect to fixed and network drives in an effort to replicate.

Protection

• Virus Definitions (Intelligent Updater) December 26, 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
• Large Scale E-mailing: All MAPI address lists
• Modifies Files: Autoexec.bat

Distribution

• Distribution Level: High
• Subject of Email: Anti-Virus Warning!!!
• Name of Attachment: sircamremover.txt[10 spaces].vbe
• Size of Attachment: 2562

TECHNICAL DETAILS

When executed, VBS.Breberka.B@mm does the following:

It checks for the existence of the following registry key before attempting to activate its payloads:

HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersionSymantec

with a value of:

...by gl

If this registry key does not exist, the worm creates a copy of itself as the following files:

• %Windows%Antivirus.vbe
• %Windows%Nimdafix.vbe
• %Temporary%Sircamremover.txt <10 blank spaces> .vbe

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

It then sends email to all entries in all MAPI address books and creates the Symantec registry key to prevent future activation.

Next, it adds the value:

SysHelp / StartUp     C:Windowscoderedhelp.vbe

to the registry key

HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersionRun

This will cause the worm to execute each time that you start Windows.

The worm then attempts to connect to all fixed and network drives, and it creates two files in the root folders of these drives:

• A 16-byte file named Dropper.com
• A copy of the worm named Symantec.txt <10 spaces> .vbe

Finally, the worm attempts to modify any file named Autoexec.bat that is found on any of the drives, so that Dropper.com is run when Windows starts.

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 worm, delete files that are detected as VBS.Breberka.B@mm, delete the Dropper.com file, restore the Autoexec.bat file, and reverse the changes that the worm made to the registry.

To remove the worm:

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. Delete all files that are detected as VBS.Breberka.B@mm.
5. Using Windows Explorer, locate and delete the file C:Dropper.com.
6. If the Autoexec.bat has been modified by the worm, restore it from a known clean backup.

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_MACHINESoftwareMicrosoftWindowsCurrentVersionSymantec
   
4. In the right pane, delete the following value:
   
   ...by gl
   
5. Navigate to the following key:
   
   HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersionRun
   
6. In the right pane, delete the following value:
   
   SysHelp / StartUp     C:Windowscoderedhelp.vbe
   
7. Click Registry, and click Exit.