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Published Nov 27, 2006 | Updated Nov 27, 2006

Win32/Bobax.O@mm

Detected by Microsoft Defender Antivirus

Aliases: Bobax.O (Symantec)

Summary

Win32/Bobax.O@mm is a mass-mailing network worm that targets computers running certain versions Microsoft Windows. The worm targets computers running Windows 2000 by exploiting the Windows Plug-and-Play buffer overflow vulnerability that is fixed with Microsoft Security Bulletin MS05-039. The worm can also send a copy of itself as an e-mail attachment to e-mail addresses that it gathers from the infected computer.
To manually recover from infection by Win32/Bobax.O@mm, follow these steps:
  1. Install security update MS05-039.
  2. Disconnect from the Internet.
  3. End the worm process.
  4. Delete the worm files from your computer.
  5. Delete the worm registry entries.
  6. Clean the Windows system hosts file.
  7. Reset the Windows XP firewall.
  8. Restart your computer.
  9. Take steps to prevent re-infection.

Install security update MS05-039

To install MS05-039 using Windows Update
  1. Go to the Windows Update Web site at windowsupdate.microsoft.com.
  2. On the Windows Update site, click Scan for Updates. Windows Update scans your computer and returns a list of critical updates, including service packs.
  3. In the Pick updates to install list, click Critical Updates and Service Packs. Windows Update creates a list of the updates appropriate for your computer, including MS05-039 if it is not installed. Critical updates are selected for download automatically.
  4. Click Review and install updates, and then click Install Now. You may need to restart your computer after installing the updates.

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.

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 each of the following processes that is running and click End Process: services.exe, nb32ext2.exe, msdefr.exe.

Delete the worm files from your computer

To delete the worm files from your computer
  1. Click Start, and click Run.
  2. In the Open field, type the name of the Windows folder, for example, C:\Windows
  3. Click OK.
  4. Click Name to sort files by name.
  5. Delete any of the following files in the list: services.exe, nb32ext2.exe, or msdefr.exe.
  6. On the Desktop, right-click the Recycle Bin and click Empty Recycle Bin.
  7. Click Yes.
If deleting any of the files fails, follow these steps to verify that the file processes are 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 services.exe, nb32ext2.exe, and msdefr.exe are not in the list.

Delete the worm registry entries

Win32/Bobax.O@mm creates entries in the Windows registry that attempt to run the worm every time your computer restarts. These entries should be deleted.
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 NT\CurrentVersion\Winlogon
  4. In the right pane, right-click the following value, if it exists:
    Userinit = C:\Windows\userinit.exe
    or
    Userinit = C:\Windows\services.exe
  5. Click Delete and click Yes to confirm the deletion.
  6. In the left pane, navigate to the key:
    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
  7. In the right pane, right-click the following value, if it exists:
    RPCserv32g = C:\Windows\services.exe
  8. Click Delete and click Yes to confirm the deletion.
  9. In the left pane, navigate to the key:
    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\RunServices
  10. In the right pane, right-click the following value, if it exists:
    helloworld = nb32ext2.exe
  11. Click Delete and click Yes to confirm the deletion.
  12. Close the Registry Editor.

Reset the Windows XP firewall

To turn on the Internet Connection Firewall in Windows XP
  1. Click Start, and click Control Panel.
  2. Click Network and Internet Connections, and click Network Connections. If you do not see Network and Internet Connections, click Switch to Category View.
  3. Highlight a connection that you want to help protect, and click Change settings of this connection.
  4. Click Advanced, and select Protect my computer and network by limiting or preventing access to this computer from the Internet.
  5. Click OK.

Clean the Windows system hosts file

The worm modifies the system hosts file to prevent access to certain Web sites.
To clean the system host file
  1. On the Start menu, click Run.
  2. Type notepad.exe and click OK.
  3. On the File menu, click Open…
  4. In the File name text box, type the name of the Windows folder and then type \system32\drivers\etc\hosts, for example, C:\Winnt\System32\drivers\etc\hosts.
  5. Search for text that begins with "127.0.0.1 avp.com…"
  6. Select this text and all text that follows. Delete the selected text and save the file.
  7. Close Notepad.

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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