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Backdoor:Win32/Rbot.MA


Backdoor:Win32/Rbot.MA is a backdoor Trojan that targets computers running certain versions of Microsoft Windows. The Trojan connects to an IRC server from the infected computer to receive commands from attackers. Such commands may copy the Trojan to other computers through network shares with weak passwords, through backdoor ports opened by other malicious software, or through the Windows Plug-and-Play vulnerability described in Microsoft Security Bulletin MS05-039.


What to do now

To manually recover from infection by Backdoor:Win32/Rbot.MA, follow these steps:
  1. Install Windows security update MS05-039.
  2. Disconnect from the Internet.
  3. Restart your computer in safe mode.
  4. End the Trojan process.
  5. Delete the Trojan file from your computer.
  6. Delete the Trojan registry entries.
  7. Restart your computer.
  8. Take steps to prevent re-infection.

Install Windows 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.

Restart your computer in safe mode

To start your the 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 Trojan process

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

Delete the Trojan file from your computer

To delete the Trojan file from your computer
  1. Click Start, and click Run.
  2. In the Open field, type the name of the system folder, for example C:\Windows\System32 
  3. Click OK.
  4. Click Name to sort files by name.
  5. Delete the file pnpsrv.exe if it is in the list.
  6. On the Desktop, right-click the Recycle Bin and click Empty Recycle Bin.
  7. Click Yes to confirm the deletion.
If deleting pnpsrv.exe fails, follow these steps to verify that the file 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 the file is not in the list.

Delete the Trojan registry entries

Backdoor:Win32/Rbot.MA creates numerous entries in the Windows registry. These entries should be deleted.
To delete the Trojan 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 following value, if it exists: Windows PNP Server
  5. Click Delete and click Yes to delete the value.
  6. Repeat steps 3 through 5 for each of the following registry keys:
    HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\RunServices
    HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\RunServices
    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\OLE
    HKEY_CURRENT_USER\SOFTWARE\Microsoft\OLE
    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa
    HKEY_CURRENT_USER\SYSTEM\CurrentControlSet\Control\Lsa
  7. 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.

Threat behavior

When Backdoor:Win32/Rbot.MA runs, it can take the following actions:
  • Copy itself as a new file to <system folder>\pnpsrv.exe.
  • Run the Trojan copy, <system folder>\pnpsrv.exe, which can then take the following actions:
    • Create the value: Windows PNP Server
      with data: pnpsrv.exe
      in each of the following registry keys:
      HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
      HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
      HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\RunServices
      HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\RunServices
      HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\OLE
      HKEY_CURRENT_USER\SOFTWARE\Microsoft\OLE
      HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa
      HKEY_CURRENT_USER\SYSTEM\CurrentControlSet\Control\Lsa
    • Open and monitor TCP port 113.
    • Connect to a specific IRC server and channel to enable attackers to perform functions such as the following:
      • Gather data, including system information, file information, and Windows clipboard contents.
      • Start a command shell and run commands.
      • Conduct denial of service (DoS) attacks against certain Web sites.
      • Visit certain Web sites and download files.
      • Copy the Trojan to other computers by the following means:
        • Through backdoor ports opened by other families of malicious software.
        • Through network shares with weak user names and passwords.
        • Using a command shell that it creates on a remote computer. It creates the shell by exploiting the Windows Plug and Play vulnerability described in Microsoft Security Bulletin MS05-039. The Trojan uses the command shell to copy itself to the remote computer and then creates a task to run the copy there.

Symptoms

There are no readily apparent indications that your computer is infected with Backdoor:Win32/Rbot.MA. However, your computer may be infected by this Trojan if you notice any of the following symptoms:
  • Presence of the file <system folder>\pnpsrv.exe.
  • Presence of value: Windows PNP Server
    with data: pnpsrv.exe
    in the following registry keys:
    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\RunServices
    HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\RunServices
    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\OLE
    HKEY_CURRENT_USER\SOFTWARE\Microsoft\OLE
    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa
    HKEY_CURRENT_USER\SYSTEM\CurrentControlSet\Control\Lsa
  • The Processes tab in Windows Task Manager shows that process pnpsrv.exe is running.
  • The executable file pnpsrv.exe is running as a service.

Prevention


Alert level: Severe
First detected by definition: 1.45.287.0
Latest detected by definition: 1.69.152.0 and higher
First detected on: Oct 07, 2008
This entry was first published on: Aug 15, 2005
This entry was updated on: Sep 19, 2006

This threat is also detected as:
No known aliases