Symantec Security Response

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W32.Wargbot

Risk Level 2: Low

Discovered: August 12, 2006
Updated: February 13, 2007 12:58:13 PM
Also Known As: CME-762 [Common Malware Enumer, CME-482 [Common Malware Enumer, WORM_IRCBOT.JK [Trend], WORM_IRCBOT.JL [Trend], IRC-Mocbot!MS06-040 [McAfee], Cuebot.J [Computer Associates], W32/Cuebot-L [Sophos], W32.Mocbot.B
Type: Worm
Systems Affected: Windows 2000, Windows 95, Windows 98, Windows Me, Windows NT, Windows Server 2003, Windows XP

SUMMARY



W32.Wargbot is a network-aware worm that opens an IRC back door on the compromised computer. It spreads by exploiting the Microsoft Windows Server Service Remote Buffer Overflow Vulnerability (as described in Microsoft Security Bulletin MS06-040). The Trojan may download a copy of Backdoor.Ranky.X.

Note: Definitions prior to August 13, 2006 may detect this as Backdoor.IRC.bot or W32.Mocbot.B.

Protection

  • Initial Rapid Release version August 13, 2006
  • Latest Rapid Release version January 23, 2010 revision 021
  • Initial Daily Certified version August 13, 2006
  • Latest Daily Certified version January 23, 2010 revision 023
  • Initial Weekly Certified release date August 16, 2006

Click here for a more detailed description of Rapid Release and Daily Certified virus definitions.

Threat Assessment

Wild

  • Wild Level: Low
  • Number of Infections: 0 - 49
  • Number of Sites: 0 - 2
  • Geographical Distribution: Low
  • Threat Containment: Easy
  • Removal: Easy

Damage

  • Damage Level: Medium

Distribution

  • Distribution Level: High

TECHNICAL DETAILS


When W32.Wargbot is executed, it performs the following actions:
  1. Copies itself as the following file:

    %System%\wgareg.exe

    Note: %System% is a variable that refers to the System folder. By default this is C:\Windows\System (Windows 95/98/Me), C:\Winnt\System32 (Windows NT/2000), or C:\Windows\System32 (Windows XP).

  2. Creates a service with the following characteristics:

    DisplayName: Windows Genuine Advantage Registration Service
    ImagePath: %System%\wgareg.exe

  3. Creates the following registry subkey in order to create the above service:

    HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\wgareg

  4. Adds the value:

    "enabledcom" = "n"

    to the registry subkey:

    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Ole

    in order to disable DCOM.

  5. Adds the values:

    "restrictanonymous" = "1"
    "restrictanonymoussam" = "1"

    the following registry entry:

    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa

    to modify access to Network shares.
  6. Adds the values:

    "autoshareserver" = "0"
    "autosharewks" = "0"

    to the following registry entry:

    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\lanmanserver
    \parameters

  7. Adds the values:

    "antivirusdisablenotify" = "1"
    "antivirusoverride" = "1"
    "firewalldisablenotify" = "1"
    "firewalldisableoverride" = "1"

    to the following registry entry:

    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Security Center

    to lower security settings.

  8. Adds the value:

    "enablefirewall" = "0"

    to the following registry entry:

    HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\windowsfirewall
    \domainprofile

    to lower security settings.

  9. Adds the value:

    "enablefirewall" = "0"

    to the following registry entry:

    HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\windowsfirewall
    \standardprofile

    to lower security settings.

  10. Adds the value:

    "Start" = "4"

    to the following registry entry:

    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SharedAccess

    to modify the Windows Firewall.

  11. Injects a program into the following process:

    explorer.exe

    in order to delete the original worm file.

  12. Creates the following file:

    %Windir%\debug\dcpromo.log

    Note: %Windir% is a variable that refers to the Windows installation folder. By default, this is C:\Windows or C:\Winnt.

  13. Opens a back door on the compromised computer by connecting to the following IRC domains on TCP port 18067:

    • [http://]bniu.hous[REMOVED].com
    • [http://]ypgw.walll[REMOVED].com

  14. Listens for commands, which may allow a remote attacker to perform some of the following actions on the compromised computer:

    • Launch denial of service attacks
    • Scan IP addresses to find computers to attack
    • Download and execute remote files
    • Send a message using AOL Instant Messenger (if it's running)
    • Remotely run the command prompt shell, which allows the attacker to run any command

  15. May receive commands to download a file from [http://]media.pixpond.com/l9rd[REMOVED]. The downloaded file is a copy of Backdoor.Ranky.X, which listens for commands from a remote attacker on a random port and sends the IP address of the compromised computer to a server on the yu.haxx.biz domain.

  16. Attempts to spread by exploiting the Microsoft Windows Server Service Remote Buffer Overflow Vulnerability (as described in Microsoft Security Bulletin MS06-040) once it receives the appropriate command. The exploit code affects computers using the Windows 2000 operating system.


Recommendations

Symantec Security Response encourages all users and administrators to adhere to the following basic security "best practices":

  • Use a firewall to block all incoming connections from the Internet to services that should not be publicly available. By default, you should deny all incoming connections and only allow services you explicitly want to offer to the outside world.
  • Enforce a password policy. Complex passwords make it difficult to crack password files on compromised computers. This helps to prevent or limit damage when a computer is compromised.
  • Ensure that programs and users of the computer use the lowest level of privileges necessary to complete a task. When prompted for a root or UAC password, ensure that the program asking for administration-level access is a legitimate application.
  • Disable AutoPlay to prevent the automatic launching of executable files on network and removable drives, and disconnect the drives when not required. If write access is not required, enable read-only mode if the option is available.
  • Turn off file sharing if not needed. If file sharing is required, use ACLs and password protection to limit access. Disable anonymous access to shared folders. Grant access only to user accounts with strong passwords to folders that must be shared.
  • Turn off and remove unnecessary services. By default, many operating systems install auxiliary services that are not critical. These services are avenues of attack. If they are removed, threats have less avenues of attack.
  • If a threat exploits one or more network services, disable, or block access to, those services until a patch is applied.
  • Always keep your patch levels up-to-date, especially on computers that host public services and are accessible through the firewall, such as HTTP, FTP, mail, and DNS services.
  • Configure your email server to block or remove email that contains file attachments that are commonly used to spread threats, such as .vbs, .bat, .exe, .pif and .scr files.
  • Isolate compromised computers quickly to prevent threats from spreading further. Perform a forensic analysis and restore the computers using trusted media.
  • Train employees not to open attachments unless they are expecting them. Also, do not execute software that is downloaded from the Internet unless it has been scanned for viruses. Simply visiting a compromised Web site can cause infection if certain browser vulnerabilities are not patched.
  • If Bluetooth is not required for mobile devices, it should be turned off. If you require its use, ensure that the device's visibility is set to "Hidden" so that it cannot be scanned by other Bluetooth devices. If device pairing must be used, ensure that all devices are set to "Unauthorized", requiring authorization for each connection request. Do not accept applications that are unsigned or sent from unknown sources.
  • For further information on the terms used in this document, please refer to the Security Response glossary.

REMOVAL


The following instructions pertain to all current and recent Symantec antivirus products, including the Symantec AntiVirus and Norton AntiVirus product lines.
  1. Disable System Restore (Windows Me/XP).
  2. Update the virus definitions.
  3. Run a full system scan.
  4. Delete any values added to the registry.
  5. Restore the Windows Security Center.
  6. Find and stop the service.
  7. Reenable the SharedAccess service (Windows 2000/XP only)
For specific details on each of these steps, read the following instructions.

1. To disable System Restore (Windows Me/XP)
If you are running Windows Me or Windows XP, we recommend that you temporarily turn off System Restore. Windows Me/XP uses this feature, which is enabled by default, to restore the files on your computer in case they become damaged. If a virus, worm, or Trojan infects a computer, System Restore may back up the virus, worm, or Trojan on the computer.

Windows prevents outside programs, including antivirus programs, from modifying System Restore. Therefore, antivirus programs or tools cannot remove threats in the System Restore folder. As a result, System Restore has the potential of restoring an infected file on your computer, even after you have cleaned the infected files from all the other locations.

Also, a virus scan may detect a threat in the System Restore folder even though you have removed the threat.

For instructions on how to turn off System Restore, read your Windows documentation, or one of the following articles:
Note: When you are completely finished with the removal procedure and are satisfied that the threat has been removed, reenable System Restore by following the instructions in the aforementioned documents.

For additional information, and an alternative to disabling Windows Me System Restore, see the Microsoft Knowledge Base article: Antivirus Tools Cannot Clean Infected Files in the _Restore Folder (Article ID: Q263455).

2. To update the virus definitions
Symantec Security Response fully tests all the virus definitions for quality assurance before they are posted to our servers. There are two ways to obtain the most recent virus definitions:
  • Running LiveUpdate, which is the easiest way to obtain virus definitions:
    • If you use Norton AntiVirus 2006, Symantec AntiVirus Corporate Edition 10.0, or newer products, LiveUpdate definitions are updated daily. These products include newer technology.
    • If you use Norton AntiVirus 2005, Symantec AntiVirus Corporate Edition 9.0, or earlier products, LiveUpdate definitions are updated weekly. The exception is major outbreaks, when definitions are updated more often.
  • Downloading the definitions using the Intelligent Updater: The Intelligent Updater virus definitions are posted daily. You should download the definitions from the Symantec Security Response Web site and manually install them. To determine whether definitions for this threat are available by the Intelligent Updater, refer to Virus Definitions (Intelligent Updater).

    The latest Intelligent Updater virus definitions can be obtained here: Intelligent Updater virus definitions. For detailed instructions read the document: How to update virus definition files using the Intelligent Updater.

3. To run a full system scan
  1. Start your Symantec antivirus program and make sure that it is configured to scan all the files.
  2. Run a full system scan.
  3. If any files are detected, follow the instructions displayed by your antivirus program.

Important: If you are unable to start your Symantec antivirus product or the product reports that it cannot delete a detected file, you may need to stop the risk from running in order to remove it. To do this, run the scan in Safe mode. For instructions, read the document, How to start the computer in Safe Mode. Once you have restarted in Safe mode, run the scan again.

After the files are deleted, restart the computer in Normal mode and proceed with the next section.

Warning messages may be displayed when the computer is restarted, since the threat may not be fully removed at this point. You can ignore these messages and click OK. These messages will not appear when the computer is restarted after the removal instructions have been fully completed. The messages displayed may be similar to the following:

Title: [FILE PATH]
Message body: Windows cannot find [FILE NAME]. Make sure you typed the name correctly, and then try again. To search for a file, click the Start button, and then click Search.

4. To delete the value from the registry
Important: Symantec strongly recommends that you back up the registry before making any changes to it. Incorrect changes to the registry can result in permanent data loss or corrupted files. Modify the specified subkeys only. For instructions refer to the document: How to make a backup of the Windows registry.
  1. Click Start > Run.
  2. Type regedit
  3. Click OK.

    Note: If the registry editor fails to open the threat may have modified the registry to prevent access to the registry editor. Security Response has developed a tool to resolve this problem. Download and run this tool, and then continue with the removal.

  4. Navigate to the subkey:

    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Ole
  5. In the right pane, restore the following entry to its previous value:

    "enabledcom" = "n"

  6. Navigate to the subkey:

    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa
  7. In the right pane, restore the following entries to their previous values:

    "restrictanonymous" = "1"
    "restrictanonymoussam" = "1"

  8. Navigate to the subkey:

    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services
    \lanmanserver\parameters
  9. In the right pane, restore the following entries to their previous values:

    "autoshareserver" = "0"
    "autosharewks" = "0"

  10. Navigate to and delete the subkey:

    HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\wgareg

  11. Exit the Registry Editor.

5. To restore the Windows Security Center
This risk attempts to disable the features in the Windows Security Center, available in Windows XP Service Pack 2. If you are running Windows XP Service Pack 2 and would like to restore the full functionality of the Windows Security Center, please complete the following steps:

Important: If your computer is connected to a domain, you may not be able to adjust these settings. If so, contact your network administrator for more information.
  1. Click Start > Control Panel.
  2. Double-click the Security Center.
  3. In the right pane, click Windows Firewall. The Windows Firewall appears.
  4. Select On.
  5. Click OK to close the Windows Firewall.
  6. In the left pane of the Security Center, select Change the way Security Center alerts me.
  7. Click Alert Settings.
  8. Select Alert Settings, Firewall, and Virus Protection.
  9. Click OK
  10. Click Automatic Updates.
  11. Select Automatic.
  12. Click OK.
  13. Exit the Security Center.

6. To find and stop the service
  1. Click Start > Run.
  2. Type services.msc, and then click OK.
  3. Locate and select the service that was detected.
  4. Click Action > Properties.
  5. Click Stop.
  6. Change Startup Type to Manual.
  7. Click OK and close the Services window.
  8. Restart the computer.
7. To reenable the SharedAccess service (Windows 2000/XP only)
The SharedAccess service is responsible for maintaining Internet Connection Sharing and the Windows Firewall/Internet Connection Firewall applications in Windows. (The presence and names of these applications vary depending on the operating system and service pack you are using.) To protect your computer and maintain network functionality, re-enable this service if you are using any of these programs.


Windows XP Service Pack 2
If you are running Windows XP with Service Pack 2 and are using the Windows Firewall, the operating system will alert you when the SharedAccess service is stopped, by displaying an alert balloon saying that your Firewall status is unknown. Perform the following steps to ensure that the Windows Firewall is re-enabled:
  1. Click Start > Control Panel.

  2. Double-click the Security Center.

  3. Ensure that the Firewall security essential is marked ON.

    Note: If the Firewall security essential is marked on, your Windows Firewall is on and you do not need to continue with these steps.

    If the Firewall security essential is not marked on, click the "Recommendations" button.

  4. Under "Recommendations," click Enable Now. A window appears telling you that the Windows Firewall was successfully turned on.

  5. Click Close, and then click OK.

  6. Close the Security Center.


Windows 2000 or Windows XP Service Pack 1 or earlier
Complete the following steps to re-enable the SharedAccess service:
  1. Click Start > Run.
  2. Type services.msc

    Then click OK.

  3. Do one of the following:
    • Windows 2000: Under the Name column, locate the "Internet Connection Sharing (ICS)" service and double-click it.
    • Windows XP: Under the Named column, locate the "Internet Connection Firewall (ICF) / Internet Connection Sharing (ICS)" service and double-click it.

  4. Under "Startup Type:", select "Automatic" from the drop-down menu.

  5. Under "Service Status:", click the Start button.

  6. Once the service has completed starting, click OK.

  7. Close the Services window.



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