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Published Feb 11, 2005 | Updated Sep 15, 2017

Worm:Win32/Mydoom.AO@mm

Detected by Microsoft Defender Antivirus

Aliases: W32/Mydoom.gen@MM (McAfee) Win32/Mydoom.Variant!Worm (CA)

Summary

Win32/Mydoom.AO@mm is a mass-mailing worm that targets certain versions of Microsoft Windows. The worm sends itself to e-mail addresses that it finds on the infected computer.
To manually recover from infection by Win32/Mydoom.AO@mm, perform the following steps:
  1. Disconnect from the Internet.
  2. Restart your computer in safe mode.
  3. End the worm process.
  4. Delete the worm files from your computer.
  5. Delete the worm registry entry.
  6. Restart your computer.
  7. 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, but before Windows displays graphical output.
  3. From the Windows Advanced Options Menu, select a safe mode option.

End the worm process

Ending the worm process will help stop your computer from infecting other computers as well as resolve the crashing, rebooting, and performance degradation issues caused by the worm.
To end the worm process
  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 lsasrv.exe, and click End Process.

Delete the worm files from your computer

After you end the worm process, delete the worm code from your computer.
To delete the worm files from your computer
  1. Click Start, and click Run.
  2. In the Open field, type %windir%\system32
  3. Click OK.
  4. Click Name to sort files by name.
  5. If the file lsasrv.exe is in the list, delete it.
  6. Repeat steps 1 to 5. However, in step 2, type <temp folder> instead of %windir%\system32
  7. On the Desktop, right-click the Recycle Bin and click Empty Recycle Bin .
  8. Click Yes .
If deleting the files fails, use the following steps to verify that lsasrv.exe is not 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 lsasrv.exe is not in the list.

Delete the worm registry entries

To delete the worm registry entries
  1. On the Start menu, click Run.
  2. Type regedit and click OK.
  3. In the left pane, navigate to the key:
    HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
  4. In the right pane, right-click the value: lsass
  5. Select Delete and click Yes to delete the value.
  6. Repeat step 3 to step 5 for the following registry key: 
    HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
  7. In the left pane, navigate to the key:
    HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\Winlogon
  8. In the right pane, right-click the value: Shell
  9. Select Modify.
  10. Delete <system folder>\lsasrv.exe and click OK.
  11. Close the Registry Editor.

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 Preventing Infection section for more information.
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