W32.Choke.Worm

SUMMARY

This worm uses the MSN Messenger Service (MSNMS) program to replicate; it is the second worm that is known to do so. The worm itself does nothing more than replicate, and if it is executed on a computer that does not have MSNMS installed, it simply remains resident in memory without replicating.

Protection

• Virus Definitions (Intelligent Updater) June 6, 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
• Payload Trigger: None
• Payload: None

Distribution

• Distribution Level: Low
• Name of Attachment: ShootPresidentBUSH.EXE
• Size of Attachment: 40,960 bytes
• Target of Infection: MSNMS users

TECHNICAL DETAILS

This worm spreads itself as the file ShootPresidentBUSH.exe.

When executed, the worm does the following:

1. It becomes memory resident.
2. It creates the following files:
   • C:Choke.exe (a copy of the worm).
   • C:ShootPresidentBUSH.exe (a copy of the worm).
   • C:About.txt (contains surrealistic expressions from the author).
   • C:Dalist.txt (contains list of buddies that have already been given a copy of the worm).
3. It then displays the following messages:
   
   
   
   and
   
   
   
4. After you click OK to these messages, you will not see any other output from this program. This could cause you to believe that the worm has terminated execution, when in fact it is still running on the system.

The worm hooks MSNMS in such away that when a buddy initiates a text conversation (for the first time) with an infected system, it sends the text message

President bush shooter is game that allows you to shoot Bush balzz  hahaha

along with an invitation to download a file named ShootPresidentBUSH.exe. If the buddy declines, the worm will not take no for an answer, and tries repeatedly until the buddy accepts the invitation.

The worm remembers the names of the buddies who have already been sent a copy of it, and responds with a smiley face to every line typed by that person.

The worm may, under some conditions, create a value in the registry key

HKEY_CURRENT_USERSoftwareMicrosoft
WindowsCurrentVersionRun

that references either of the executable files that it created on drive C.

This worm contains many bugs and may eventually cause the system to stop responding.

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, end its task to stop it from running, delete any files detected as W32.Choke.Worm, and undo, if necessary, the change that it made to the registry.

To stop the worm from running:

1. Press Ctrl+Alt+Delete. The Close Program dialog box appears.
2. Select the program registered as Choke, and then click End task.

To delete the worm:

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 detected as W32.Choke.Worm

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_CURRENT_USERSoftwareMicrosoft
   WindowsCurrentVersionRun
   
4. In the right pane, delete any values that point to either of the following:
   
   C:Choke.exe
   C:ShootPresidentBUSH.exe
   
5. Exit the Registry Editor.