W32.Agist.A@mm

SUMMARY

The W32.Agist.A@mm mass-mailing worm:

• Scans fixed and RAM drives.
• Scans drives C through Z for email addresses and sends itself to any email addresses found.
  The subject, body, and attachment names vary.
• The attachment will have a .zip file extension. The worm is packed using FSG.

Protection

• Virus Definitions (LiveUpdate™ Weekly) July 19, 2004
• Virus Definitions (Intelligent Updater) July 19, 2004

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: Sends email to the addresses collected from an infected computer.
• Degrades Performance: Mass-mailing may clog mail servers or degrade network performance.

Distribution

• Distribution Level: High
• Subject of Email: Varies
• Name of Attachment: Varies with .zip file extension
• Size of Attachment: 14,245 bytes

TECHNICAL DETAILS

When W32.Agist.A@mm runs, it performs the following actions:

1. Creates a mutex with the same name as the currently logged on user.
   
   
2. Copies itself to %system%<filename>.exe.
   
   The file name will have four letters, generated as follows:
   
   First letter: last letter of the currently logged on user name
   Second letter: last letter of the computer name
   Third letter: First letter of the user name
   Fourth letter: First letter of the computer name
   
   Note: %Windir% is a variable. The worm locates the Windows installation folder (by default, this is C:Windows or C:Winnt) and copies itself to that location.
   
   
3. If the infected computer runs Windows 95/98/Me, the worm will add:
   
   load=<worm filename>.exe
   
   to the [windows] section in the Win.ini file.
   
   
4. Gathers the email addresses from drives C to Z. It checks only fixed drives and RAM disks. In each drive, it searches for the email addresses in the files with the following extensions:
   
   • adb
   • tbb
   • html
   • xml
   • cfg
   • vbs
   • msg
   • dbx
   • uin
   • jsp
   • asp
   • cgi
   • php
   • sht
   • mht
   • ods
   • log
   • htm
   • mbx
   • nch
   • eml
   • txt
     
     
5. Uses its own SMTP engine to send an email to the gathered email addresses.
   
   The email will have the following properties:
   
   From: <spoofed>
   
   Subject: (blank, or one of the following)
   • Against!
   • Revenge!
     

Body: (garbage)
The email will have an attached randomly named .zip file. This .zip file contains a copy of the worm.

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

The following instructions pertain to all current and recent Symantec antivirus products, including the Symantec AntiVirus and Norton AntiVirus product lines.

1. Disable System Restore (Windows Me/XP).
2. Update the virus definitions.
3. Edit the changes made to the Win.ini file.
4. Restart the computer in Safe mode or VGA mode.
5. Run a full system scan and repair the files that are detected as W32.Agist.A@mm.
   

For details on each of these steps, read the following instructions.

1. To disable System Restore (Windows Me/XP)
   Windows Me and Windows XP users should temporarily turn off System Restore. This feature, which is enabled by default, is used by Windows Me/XP to restore files on your computer in case they become damaged. When a computer is infected with a virus, worm, or Trojan, it is possible that System Restore could back up the virus, worm, or Trojan.
   
   By default, Windows prevents System Restore from being modified by outside programs. As a result, there is the possibility that you could accidentally restore an infected file or that on-line scanners would detect the threat in that location. For instructions on how to turn off System Restore, read your Windows documentation or one of the following articles:
   • How to disable or enable Windows Me System Restore
   • How to disable or enable Windows XP System Restore
     
     
     For additional information and an alternative to disabling System Restore in Windows Me, see the Microsoft Knowledge Base article Anti-Virus Tools Cannot Clean Infected Files in the _Restore Folder (Q263455).
     
     
     Note: The contents of the System Restore folder and all previous restore points will be deleted. We recommend that you re-enable System Restore after all the procedures, such as a virus removal, are complete.
     
2. To update the virus definitions
   Symantec Security Response fully tests all the virus definitions for quality assurance before they are posted to our servers. There are two ways to obtain the most recent virus definitions:
   • Running LiveUpdate, which is the easiest way to obtain virus definitions: These virus definitions are posted to the LiveUpdate servers once each week (usually on Wednesdays), unless there is a major virus outbreak. To determine whether definitions for this threat are available by LiveUpdate, refer to the Virus Definitions (LiveUpdate).
   • Downloading the definitions using the Intelligent Updater: The Intelligent Updater virus definitions are posted on U.S. business days (Monday through Friday). You should download the definitions from the Symantec Security Response Web site and manually install them. To determine whether definitions for this threat are available by the Intelligent Updater, refer to the Virus Definitions (Intelligent Updater).
     
     The Intelligent Updater virus definitions are available: Read "How to update virus definition files using the Intelligent Updater" for detailed instructions.
     
3. To Edit the Win.ini file
   If you are running Windows 95/98/Me, the function you perform depends on your operating system, follow these steps:
   • Windows 95/98: Go to step B.
   • Windows Me: If you are running Windows Me, the Windows Me file-protection process may have made a backup copy of the Win.ini file that you need to edit. If this backup copy exists, it will be in the C:WindowsRecent folder. Symantec recommends that you delete this file before continuing with the steps in this section. To do this:
     1. Start Windows Explorer.
     2. Browse to and select the C:WindowsRecent folder.
     3. In the right pane, select the Win.ini file and delete it. The Win.ini file will be regenerated when you save your changes to it in step F.
        
        
   1. Click Start > Run.
   2. Type the following:
      
      edit c:windowswin.ini
      
      and then click OK.
      
      
      Note: If Windows is installed in a different location, make the appropriate path substitution.
      
      
   3. In the [windows] section of the file, look for a line similar to:
      
      load= %system%<worm filename>.exe
      
      
   4. If this line exists, delete everything to the right of run=
      
4. To restart the computer in Safe mode or VGA mode
   Shut down the computer and turn off the power. Wait for at least 30 seconds, and then restart the computer in Safe mode or VGA mode.
   • For Windows 95, 98, Me, 2000, or XP users, restart the computer in Safe mode. For instructions, read the document, "How to start the computer in Safe Mode."
   • For Windows NT 4 users, restart the computer in VGA mode.
     
5. To scan for and delete the infected files
   1. Start your Symantec antivirus program and make sure that it is configured to scan all the files.
      • For Norton AntiVirus consumer products: Read the document, "How to configure Norton AntiVirus to scan all files."
      • For Symantec AntiVirus Enterprise products: Read the document, "How to verify that a Symantec Corporate antivirus product is set to scan all files."
   2. Run a full system scan.
   3. If any files are detected as infected with W32.Agist.A@mm, click Repair. If the repair fails, the file must be one of the dropped files. Delete the file.
   4. Restart the computer in Normal mode. For instructions, read the section on returning to Normal mode in the document, How to start the computer in Safe Mode.