VBS.Count.A.int

SUMMARY

This worm spreads by using Microsoft Outlook. It adds a value to the registry and drops a VBS file that, if run, drops a .bat file that deletes all files in the C:, C:Windows, C:Documenti, and C:Programmi folders.

Protection

• Virus Definitions (Intelligent Updater) July 16, 2001

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: Low
• Large Scale E-mailing: Sends itself to all addresses in the Microsoft Outlook address book.
• Deletes Files: All files in c:, c:windows, c:documenti, and c:programmi
• Degrades Performance: Might overload email servers

Distribution

• Distribution Level: Low
• Subject of Email: "WOW!"
• Name of Attachment: C:Windowscounsrpt.vbs
• Size of Attachment: ~1500 bytes

TECHNICAL DETAILS

This worm is a Visual Basic Script (VBS) worm that uses Microsoft Outlook to spread. It sends itself to all addresses in the Microsoft Outlook address book. It arrives as:

Subject: WOW!
Message: Check the attachement!
Attachment: C:WindowsCounsrpt.vbs

The worm adds the value

CountRunner  c:windowscounsrpt.vbs

to the registry key

HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRunCountRunner

This allows it to run as a service the next time that Windows starts. The Counsrpt.vbs file overwrites the Autoexec.bat file with a file that contains commands to delete all files in the following folders:

• C:
• C:Windows
• C:Documenti
• C:Programmi

Due to the naming of the latter two folders, the worm will only delete documents and programs on a specific non-English version of Windows. It also creates two folders on the hard drive, and makes them the A and D drives. This is to prevent you from reinstalling deleted system files from the floppy disk drive or the CD-ROM drive.

NOTE: You will only be prevented from reinstalling the deleted files when the virus is running.

It also changes your desktop wallpaper to an .html file containing the word "decrypt!" and the following string of characters:

_`g`o`^5Wrdi_jrnW^jpinmko)q]nn

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 the files detected as VBS.Count.A.int, look for and delete files in the list that follows, and undo the changes that the worm made to the registry. In some cases, you must reinstall Windows.

To remove most of the worm files:
This will remove many--but not necessarily all--of the files that were dropped:

1. Run LiveUpdate to make sure that you have the most recent virus definitions.
2. Start Norton AntiVirus (NAV), and then run a full system scan, making sure that NAV is set to scan all files.
3. Delete any files detected as VBS.Count.A.int. (We suggest that you write down the file names of the files that you delete; this will make the removal process that is described in the next section somewhat easier.)

To delete files with Windows Explorer:
Using Windows Explorer, delete any of the files in the following list that were not deleted during the NAV scan.

• C:WindowsCursorsDecrypt.html
• C:WindowsCount.cnt
• C:WindowsCounsrpt.vbs

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 then 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
   
   in the right pane, delete the value
   
   CountRunner   C:WindowsCounsrpt.vbs
   
4. Click the Registry menu, and then click Exit to save the changes.

Reinstall Windows if necessary
See your Microsoft Windows installation instructions for additional information.