Discovered: October 25, 2001
Updated: February 13, 2007 11:37:34 AM
Also Known As: W32.ElKern.3326 (dr), Win32.Elkern.a [KAV], W32/Elkern.cav.a [McAfee], PE_ELKERN.A [Trend], W32/ElKern-A [Sophos], Win32/Wqk.A [CA]
Systems Affected: Windows
W32.ElKern.3326 is a virus that infects files over open shares and mapped drives. It also tries to infect all executable files in the \Windows\System folder.
If it is activated under Windows NT/2000, then this virus crashes when it is first activated. If it is activated under Windows 9x and you have a mapped network share that is write-protected, then this virus crashes the computer after a short period of time.
Some files that become infected with this virus do not change in size.
This virus has a payload that destroys all files on locally connected drives (including mapped drives).
This payload becomes active on March 13 and September 13.
When the virus is executed, it has a very small chance of randomly activating this payload.
NOTE : This virus is associated with and can be dropped by either W32.Klez.A or W32.Klez.D . Please read those write-ups for additional information.
Symantec has provided a tool to remove infections of all known variants of W32.Klez and W32.ElKern. Click here to obtain the tool. This is the easiest way to remove these threats and should be tried first.
Note on W32.Klez.gen@mm detections:
W32.Klez.gen@mm is a generic detection for variants of W32.Klez. Computers that are infected with W32.Klez.gen@mm most likely have been exposed to either W32.Klez.E@mm or W32.Klez.H@mm. If your computer is detected as infected with W32.Klez.gen@mm , download and run the tool. In most case, the tool will be able to remove the infection.
Antivirus Protection Dates
- Initial Rapid Release version October 26, 2001
- Latest Rapid Release version April 22, 2019 revision 001
- Initial Daily Certified version October 26, 2001
- Latest Daily Certified version April 22, 2019 revision 007
- Initial Weekly Certified release date October 26, 2001
Click here for a more detailed description of Rapid Release and Daily Certified virus definitions.
Removal using the removal tool:
Symantec has provided a tool to remove infections of all known variants of W32.Klez and W32.ElKern.
Note on W32.Klez.gen@mm detections: W32.Klez.gen@mm is a generic detection for variants of W32.Klez. Computers that are infected with W32.Klez.gen@mm most likely have been exposed to either W32.Klez.E@mm or W32.Klez.H@mm. If your computer is detected as infected with W32.Klez.gen@mm , download and run the tool. In most case, the tool will be able to remove the infection.
When this virus infects files, it can behave as either a cavity infector or an appender. This means that the virus can inject itself into the host file in such a fashion as to not increase the file's overall size.
Once the virus is activated, it creates a new thread for its own execution and then gives control directly to the original host program.
The virus creates a copy of itself in the \Windows\System folder. Norton AntiVirus detects this file as W32.ElKern.3326 (dr). The file name differs, depending on the Windows version:
- Windows 95/98/Me: %System%\Wqk.exe
- Windows NT/2000: %System%\Wqk.dll
NOTE: %System% is a variable. The worm locates the \Windows\System folder (by default this is C:\Windows\System or C:\Winnt\System32), and copies itself to that location.
It then does the following, depending on the Windows version:
- Windows 95/98/Me
It adds the value
to the registry key
This causes the virus to run each time that you start Windows.
- Windows NT/2000
It adds the value
to the registry key
NOTE: When the virus searches for files to infect, this virus ignores the file extensions. The virus checks each file to see if it is a valid Windows executable before infecting it. However, it does not infect .dll files.
During the infection process this virus infects all drives on the computer (including mapped ones). This virus also searches through all available network resources for open shares, which it then tries to infect.
Due to a bug, the virus will crash a computer running Windows 9x if any of these shares are write-protected.
Symantec Security Response encourages all users and administrators to adhere to the following basic security "best practices":
- Use a firewall to block all incoming connections from the Internet to services that should not be publicly available. By default, you should deny all incoming connections and only allow services you explicitly want to offer to the outside world.
- 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.
- Ensure that programs and users of the computer use the lowest level of privileges necessary to complete a task. When prompted for a root or UAC password, ensure that the program asking for administration-level access is a legitimate application.
- Disable AutoPlay to prevent the automatic launching of executable files on network and removable drives, and disconnect the drives when not required. If write access is not required, enable read-only mode if the option is available.
- Turn off file sharing if not needed. If file sharing is required, use ACLs and password protection to limit access. Disable anonymous access to shared folders. Grant access only to user accounts with strong passwords to folders that must be shared.
- Turn off and remove unnecessary services. By default, many operating systems install auxiliary services that are not critical. These services are avenues of attack. If they are removed, threats have less avenues of attack.
- If a 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.
- Configure your email server to block or remove email that contains file attachments that are commonly used to spread threats, such as .vbs, .bat, .exe, .pif and .scr files.
- Isolate compromised computers quickly to prevent threats from spreading further. 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.
- If Bluetooth is not required for mobile devices, it should be turned off. If you require its use, ensure that the device's visibility is set to "Hidden" so that it cannot be scanned by other Bluetooth devices. If device pairing must be used, ensure that all devices are set to "Unauthorized", requiring authorization for each connection request. Do not accept applications that are unsigned or sent from unknown sources.
- For further information on the terms used in this document, please refer to the Security Response glossary.
Run LiveUpdate to make sure that you have the most recent virus definitions.
- Start Norton AntiVirus (NAV), and make sure that NAV is configured to scan all files. For instructions on how to do this, read the document How to configure Norton AntiVirus to scan all files.
- Run a full system scan.
- Click Repair for any file that is identified as being infected with W32.ElKern.3326.
- Click Delete for any file that is identified as being infected with W32.ElKern.3326 (dr).
- If you are running Windows 95/98/Me, go on the next section to remove the value that the virus added to the registry.
To edit the registry:
CAUTION : We strongly recommend that you back up the system registry before you make any changes. Incorrect changes to the registry could result in permanent data loss or corrupted files. Please make sure that you modify only the keys that are specified. Please see the document How to back up the Windows registry before you proceed.
- Click Start, and click Run. The Run dialog box appears.
- Type regedit and then click OK. The Registry Editor opens.
- Navigate to the following key:
- In the right pane, delete the following value:
- Click Registry, and click Exit
Writeup By: Atli Gudmundsson