W32.Dumaru.Gen@mm

SUMMARY

W32.Dumaru.Gen@mm is a generic detection to catch possible future variants of the W32.Dumaru family of worms. This family consists of mass-mailing threats, which may contain the following functionality:

• Keylogging
• File infection
• Remote access via backdoor

Most variants are packed with a run-time packer, such as UPX or FSG.

Protection

• Virus Definitions (LiveUpdate™ Weekly) January 26, 2004
• Virus Definitions (Intelligent Updater) January 26, 2004

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: Medium
• Large Scale E-mailing: Sends email to all the addresses harvested from specific files found on the local system.
• Releases Confidential Info: May log keystrokes and steal passwords.
• Compromises Security Settings: May allow remote access.

Distribution

• Distribution Level: High
• Subject of Email: Varies
• Name of Attachment: Varies
• Size of Attachment: Varies
• Ports: Varies

TECHNICAL DETAILS

A worm from the W32.Dumaru family typically does the following:

1. Copies itself to the %System% and %Startup% folder(s). The file names may vary.
   
   

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   Notes:
   -- %System% is a variable. The worm locates the System folder and copies itself to that location. By default, this is C:WindowsSystem (Windows 95/98/Me), C:WinntSystem32 (Windows NT/2000), or C:WindowsSystem32 (Windows XP).
   -- %Startup% is a variable: The worm retrieves the Windows startup folder and copies itself to that location. For example, this is C:WindowsStart MenuProgramsStartup in the Windows 98 system.

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2. Adds a value in the form:
   
   "<key name>" = "<the filename of the worm>"
   
   for example:
   
   "load32"="%System%l32x.exe"
   
   to the registry key:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun
   
   so that the worm runs when you start Windows.
   
   
3. Modifies the [boot] section of the System.ini file (Windows 95/98/Me only) as follows:
   
   [boot]
   shell=explorer.exe <the filename of the worm>
   
   so that the worm runs when you start Windows 95/98/Me.
   
   
4. May create the registry key:
   
   HKEY_LOCAL_MACHINESOFTWARESARS
   
   this serves as an infection marker for the worm, which will determine whether a certain functionality is executed.
   
   
5. Modifies the Value data of: Shell
   
   in the registry key:
   
   HKEY_LOCAL_MACHINESoftwareMicrosoftWindows NTCurrentVersionWinlogon
   
   from:
   
   "explorer.exe"
   
   to:
   
   "explorer.exe <the filename of the worm>"
   
   so that the worm runs when you start Windows NT/2000/XP.
   
   
6. Retrieves email addresses from the system by parsing from the files that match a particular set of file extensions.
   
   For example:
   • .htm
   • .wab
   • .html
   • .dbx
   • .tbb
   • .abd
     
     The email addresses will be saved to a file on the local system, which will not be detected.
     
     
7. Uses its own SMTP engine to email itself to the addresses it finds. The email may have a spoofed "From" address.
   

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. Restart the computer in Safe mode or VGA mode.
4. Run a full system scan and delete all the files detected as W32.Dumaru.Gen@mm.
5. Reverse the changes that were made to the registry.
6. Edit the System.ini file (Windows 95/98/Me).
   

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

1. Disabling System Restore (Windows Me/XP)
If you are running Windows Me or Windows XP, we recommend that you temporarily turn off System Restore. Windows Me/XP uses this feature, which is enabled by default, to restore the files on your computer in case they become damaged. If a virus, worm, or Trojan infects a computer, System Restore may back up the virus, worm, or Trojan on the computer.

Windows prevents outside programs, including antivirus programs, from modifying System Restore. Therefore, antivirus programs or tools cannot remove threats in the System Restore folder. As a result, System Restore has the potential of restoring an infected file on your computer, even after you have cleaned the infected files from all the other locations.

Also, a virus scan may detect a threat in the System Restore folder even though you have removed the threat.

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 turn off or turn on Windows XP System Restore"

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Note: When you are completely finished with the removal procedure and are satisfied that the threat has been removed, re-enable System Restore by following the instructions in the aforementioned documents.

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For additional information, and an alternative to disabling Windows Me System Restore, see the Microsoft Knowledge Base article, "Antivirus Tools Cannot Clean Infected Files in the _Restore Folder," Article ID: Q263455.

2. Updating 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. Restarting 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.

4. Scanning for and deleting 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.Dumaru.Gen@mm, write down the file names, and then click Delete.

5. Reversing the changes that were made to the registry.

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WARNING: Symantec strongly recommends that you back up the registry before making any changes to it. Incorrect changes to the registry can result in permanent data loss or corrupted files. Modify the specified keys only. Read the document, "How to make a backup of the Windows registry," for instructions.

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1. Click Start, and then click Run. (The Run dialog box appears.)
2. Type regedit
   
   Then click OK. (The Registry Editor opens.)
   
   
3. Navigate to the key:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun
   
   
4. In the right pane, delete any values that refer to the worm files, which were detected in step 3.
   
   
5. Do one of the following:
   • If you are using Windows 95/98/Me, skip to step i.
   • If you are using Windows NT/2000/Xp, go on to step f.
     
     
6. Navigate to the key:
   
   HKEY_LOCAL_MACHINESoftwareMicrosoftWindows NTCurrentVersionWinlogon
   
   
7. In the right pane, double-click: Shell
   
   
8. Change:
   
   "explorer.exe %Windir%system32vxd32v.exe"
   
   to:
   
   "explorer.exe"
   
   
9. Exit the Registry Editor.
   
   
10. Restart the computer into Normal mode. For instructions, read the section on returning to Normal mode in the document, "How to start the computer in Safe Mode."

6. Editing the System.ini file
If you are running Windows 95/98/Me, follow these steps:

1. The function you perform depends on your operating system:
   • 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 System.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 System.ini file and delete it. The System.ini file will be regenerated when you save your changes to it in step F.
        
        
2. Click Start, and then click Run.
   
   
3. Type the following, and then click OK.
   
   edit c:windowssystem.ini
   
   (The MS-DOS Editor opens.)
   
   NOTE: If Windows is installed in a different location, make the appropriate path substitution.
   
   
4. In the [boot] section of the file, look for a line similar to:
   
   shell = Explorer.exe C:WINDOWSSYSTEM<file name of worm>
   
   
5. If this line exists, delete everything to the right of Explorer.exe.
   
   When you are done, it should look like:
   
   shell = Explorer.exe
   
   
6. Click File, and then click Save.
   
   
7. Click File, and then click Exit.