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Published May 08, 2006 | Updated Sep 15, 2017

Worm:Win32/Plexus.A@mm

Detected by Microsoft Defender Antivirus

Aliases: No associated aliases

Summary

Win32/Plexus.A@mm is a mass-mailing e-mail worm that targets Microsoft Windows. The worm also spreads through Kazaa peer-to-peer network shares and to computers that have not been patched for the Windows vulnerabilities described in Microsoft Security Bulletins MS03-039 and MS04-011. Win32/Plexus.A@mm opens a backdoor which allows attackers to run arbitrary code on the infected computer.
To recover manually from infection by Win32/Plexus.A@mm, follow these steps:
  1. Disconnect from the Internet.
  2. Restart your computer in safe mode.
  3. End the backdoor process and worm processes.
  4. Delete the backdoor and worm files.
  5. Delete the worm registry entry.
  6. Scan with up-to-date antivirus software.
  7. Restart your computer.
  8. Take steps to prevent re-infection.

Disconnect from the Internet

To help ensure that your computer is not actively infecting other computers, disconnect it from the Internet before proceeding. Print this Web page or save a copy on your computer; then unplug your network cable and disable your wireless connection. You can reconnect to the Internet after completing these steps.

Restart your computer in safe mode

To start your computer in safe mode
  1. Remove all floppy disks and CDs from your computer, and then restart your computer.
  2. When prompted, press F8. If Windows starts without displaying the Please select the operating system to start menu, restart your computer. Press F8 after the firmware POST process completes and before Windows displays graphical output.
  3. From the Windows Advanced Options menu, select a safe mode option.

End the backdoor process and worm processes

To end the processes
  1. Press CTRL+ALT+DEL once and click Task Manager.
  2. Click Processes and click Image Name to sort the running processes by name.
  3. Select the process _pu.exe if it exists, and click End Process.
  4. Select the process upu.exe if it exists, and click End Process.

Delete the backdoor and worm files

To delete the backdoor and worm files
  1. Click Start, and click Run.
  2. In the Open field, type %temp%
  3. Click OK.
  4. Click Name to sort files by name.
  5. If _up.exe is in the list, delete it.
  6. Click Start, and click Run.
  7. In the Open field, type the path to the Windows system folder. (For Windows NT-based systems such as Windows 2000 or Windows XP, the path to the system folder is %windir%\System32; for other Windows systems such as Windows 98 or Windows ME, the path is %windir%\System.)
  8. Click OK.
  9. Click Name to sort files by name.
  10. If the file name upu.exe is in the list, delete it.
  11. Click Start.
  12. Click Search, and click For Files or Folders…The Search Results window appears.
  13. In the left pane of the Search Results window:
    1. Under What do you want to search for?, click All Files and Folders.
    2. In the Look in: box, click Local Hard Drives.
    3. In the All or part of the file name box, type AVP5.xcrack.exe.
  14. Click Search.
  15. When the search finishes, if the file AVP5.xcrack.exe is in the results list, delete it.
  16. In the left pane, click Back.
  17. Repeat steps 13c through 16 for each of the possible worm-file names. To do so, on each iteration, replace the file name you last used in step 13c (such as AVP5.xcrack.exe) with the next file name from the following list. Ensure that you type each file name correctly:
    hx00def.exe
    ICQBomber.exe
    InternetOptimizer1.05b.exe
    Shrek_2.exe
    UnNukeit9xNTICQ04noimageCrk.exe
    YahooDBMails.exe
  18. On the Desktop, right-click the Recycle Bin and click Empty Recycle Bin.
  19. Click Yes to confirm.
If deleting any of the file(s) fails, follow these steps to verify that the none of the corresponding processes is running:
  1. Press CTRL+ALT+DEL once and click Task Manager.
  2. Click Processes and click Image Name to sort the running processes by name.
  3. Confirm that none of the files you attempted to delete is in the list.

Delete the worm registry entry

Win32/Plexus.A@mm creates an entry in the Windows registry that attempts to run the worm automatically each time Windows starts. This entry should be deleted.
To delete the worm registry entry
  1. On the Start menu, click Run.
  2. Type regedit and click OK.
  3. In the left pane, navigate to the key:
    HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
  4. In the right pane, right-click the following value, if it exists: NvClipRsv
  5. Click Delete and click Yes to delete the value.
  6. Close the Registry Editor.

Scan with antivirus software

Win32/Plexus.A@mm opens a backdoor that can download other malicious software to your computer. To recover from this additional malicious software, you must run a full-system scan with an up-to-date antivirus product. Several companies provide antivirus software for this purpose. For more information, see http://www.microsoft.com/athome/security/downloads/default.mspx

Restart your computer

To restart your computer
  1. On the Start menu, click Shut Down.
  2. Select Restart from the drop-down list and click OK.

Take steps to prevent re-infection

Do not reconnect your computer to the Internet until the computer is protected from re-infection. See the section on "How to Prevent Infection" for more information.
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