VBS.Potok@mm

SUMMARY

The VBS.Potok@mm worm is a simple Visual Basic script that exploits a little-known feature of Windows NT/2000 to spread. It sends itself to the first 50 recipients in the Microsoft Outlook Address Book. It attempts to add a new user to the infected computer and grant the user Administrator rights. The sample of this worm the Symantec AntiVirus Research Center (SARC) received has bugs that prevent it from operating correctly.

Protection

• Virus Definitions (LiveUpdate™ Weekly) July 30, 2001
• Virus Definitions (Intelligent Updater) July 30, 2001

Threat Assessment

Wild

• Wild Level: Low
• Number of Infections: 50 - 999
• Number of Sites: 3 - 9
• Geographical Distribution: Medium
• Threat Containment: Easy
• Removal: Moderate

Damage

• Damage Level: Low
• Large Scale E-mailing: Send mesages to first 50 recipients in Outlook Address Book
• Compromises Security Settings: Attempts to add New Administrative account for the virus writer.

Distribution

• Distribution Level: High
• Subject of Email: New Generation of drivers.
• Name of Attachment: driver.doc .vbs The filename has 46 spaces within itself.
• Size of Attachment: 9262 bytes

TECHNICAL DETAILS

The worm exploits a little-known feature of Windows NT/2000: file streams. Under Windows NT/2000, a file can contain multiple streams of data. This is similar to a compressed archive file that contains multiple files. Each stream is accessible as an individual file. On a computer that is running Windows 95/98/Me with the FAT or FAT32 file system, these streams do not exist. Therefore, on a computer that is running Windows 95/98/Me, the worm is not able to run the parts of itself that attempt to add new users to the system.

The worm has four streams: a mail stream, a user stream, a main stream, and a group stream.

• The mail stream attempts to send the worm to the first 50 recipients in the Microsoft Outlook Address Book.
• The user stream attempts to create a new account on the system.
• The main stream attempts to access the new account.
• The group stream attempts to add the new user to the Administrator group.

The worm adds these four streams to a file named Odbc.ini that is created in the Windows folder. It drops Notepad.vbs into the WinntSystem32Ras folder. The file Go.vbs is also created in the WinntSystem32 folder.

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

1. Run LiveUpdate to make sure that you have the most recent virus definitions.
2. Start Norton AntiVirus (NAV), and run a full system scan, making sure that NAV is set to scan all files.
3. Delete any files that are detected as VBS.Potok@mm.
4. If the file Odbc.ini is detected as infected, delete it.
5. If a new, unrecognized Administrator account exists, delete the account.