Virus alert about the Win32/Conficker.B worm

If your computer is infected with this worm, you may not experience any symptoms, or you may experience any of the following symptoms:

* Account lockout policies are being tripped.
* Automatic Updates, Background Intelligent Transfer Service (BITS), Windows Defender, and Error Reporting Services are disabled.
* Domain controllers respond slowly to client requests.
* The network is congested.
* Various security-related Web sites cannot be accessed.


Win32/Conficker.B has multiple propagation methods. These include the following:

* Exploitation of the vulnerability that is patched by security update 958644 (MS08-067)
* The use of network shares
* The use of AutoPlay functionality

Therefore, you must be careful when you clean a network so that the threat is not reintroduced to systems that have previously been cleaned.



Stop Conficker from spreading by using Group Policy
Notes

* This procedure does not remove the Conficker malware from the system. This procedure only stops the spread of the malware. You should use an antivirus product to remove the Conficker malware from the system. Or, follow the steps in the "Manual steps to remove the Conficker.b variant" section of this Knowledge Base article to manually remove the malware from the system.
* Please carefully read and understand the note in step 4 of this procedure.

Create a new policy that applies to all computers in a specific organizational unit (OU), site, or domain, as required in your environment.

To do this, follow these steps:

1. Set the policy to remove write permissions to the following registry subkey:
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\Svchost
This prevents the random named malware service from being created in the netsvcs registry value.

To do this, follow these steps:
1. Open the Group Policy Management Console (GPMC).
2. Create a new Group Policy object (GPO). Give it any name that you want.
3. Open the new GPO, and then move to the following folder:
Computer Configuration\Windows Settings\Security Settings\Registry
4. Right-click Registry, and then click Add Key.
5. In the Select Registry Key dialog box, expand Machine, and then move to the following folder:
Software\Microsoft\Windows NT\CurrentVersion\Svchost
6. Click OK.
7. In the dialog box that opens, click to clear the Full Control check box for both Administrators and System.
8. Click OK.
9. In the Add Object dialog box, click Replace existing permissions on all subkeys with inheritable permissions.
10. Click OK.
2. Set the policy to remove write permissions to the %windir%\tasks folder. This prevents the Conficker malware from creating the Scheduled Tasks that can re-infect the system.

To do this, follow these steps:
1. In the same GPO that you created earlier, move to the following folder:
Computer Configuration\Windows Settings\Security Settings\File System
2. Right-click File System, and then click Add File.
3. In the Add a file or folder dialog box, browse to the %windir%\Tasks folder. Make sure that Tasks is highlighted and listed in the Folder: dialog box.
4. Click OK.
5. In the dialog box that opens, click to clear the check boxes for Full Control, Modify and Write for both Administrators and System.
6. Click OK.
7. In the Add Object dialog box, click Replace existing permissions on all subkeys with inheritable permissions.
8. Click OK.
3. Set AutoPlay (Autorun) features to disabled. This keeps the Conficker malware from spreading by using the AutoPlay features that are built into Windows.

To do this, follow these steps:
1. In the same GPO that you created earlier, move to one of the following folders:
* For a Windows Server 2003 domain, move to the following folder:
Computer Configuration\Administrative Templates\System
* For a Windows 2008 domain, move to the following folder:
Computer Configuration\Administrative Templates\Windows Components\Autoplay Policies
2. Open the Turn off Autoplay policy.
3. In the Turn off Autoplay dialog box, click Enabled.
4. In the drop-down menu, click All drives.
5. Click OK.
4. Disable the local administrator account. This blocks the Conficker malware from using the brute force password attack against the administrator account on the system.

Note Do not follow this step if you link the GPO to the domain controller's OU because you could disable the domain administrator account. If you have to do this on the domain controllers, create a separate GPO that does not link the GPO to the domain controller's OU, and then link the new separate GPO to the domain controller's OU.

To do this, follow these steps:
1. In the same GPO that you created earlier, move to the following folder:
Computer Configuration\Windows Settings\Security Settings\Local Policies\Security Options
2. Open Accounts: Administrator account status.
3. In the Accounts: Administrator account status dialog box, click to select the Define this policy check box.
4. Click Disabled.
5. Click OK.
5. Close the Group Policy Management Console.
6. Link the newly created GPO to the location that you want it to apply to.
7. Allow for enough time for Group Policy to update to all computers. Generally, Group Policy replication takes five minutes to replicate to each domain controller, and then 90 minutes to replicate to the rest of the systems. A couple hours should be enough. However, more time may be required, depending on the environment.
8. After the Group Policy has propagated, clean the systems of malware.

Run the Malicious Software Removal tool

The Microsoft Malware Protection Center has updated the Malicious Software Removal tool (MSRT). This is a stand-alone binary that is useful in the removal of prevalent malicious software, and it can help remove the Win32/Conficker malware family.

You can download the MSRT from either of the following Microsoft Web sites:
http://www.update.microsoft.com (http://www.update.microsoft.com)
http://support.microsoft.com/kb/890830 (http://support.microsoft.com/kb/890830)

For more information about specific deployment details for the MSRT, click the following article number to view the article in the Microsoft Knowledge Base:
891716 (http://support.microsoft.com/kb/891716/ ) Deployment of the Microsoft Windows Malicious Software Removal Tool in an enterprise environment
Note The Stand-Alone System Sweeper tool will also remove this infection. This tool is available as a component of the Microsoft Desktop Optimization Pack 6.0 or through Customer Service and Support. To obtain the Microsoft Desktop Optimization Pack, visit the following Microsoft Web site:
http://www.microsoft.com/windows/enterprise/technologies/mdop.aspx (http://www.microsoft.com/windows/enterprise/technologies/mdop.aspx)
If Windows Live OneCare or Microsoft Forefront Client Security is running on the system, these programs also block the threat before it is installed.