W32.Loxbot.F is a worm that opens a back door on the compromised computer allowing a remote attacker to issue various commands, and spreads using AOL, MSN and Yahoo Instant Messenger. The worm also lowers security on the compromised computer by disabling security related services.

Type:	Worm
Systems Affected:	Windows 2000, Windows 95, Windows 98, Windows Me, Windows NT, Windows Server 2003, Windows XP

Virus Definitions (LiveUpdate™ Plus) February 01, 2006 Virus Definitions (LiveUpdate™ Daily) February 01, 2006 Virus Definitions (LiveUpdate™ Weekly) February 01, 2006 Virus Definitions (Intelligent Updater) February 01, 2006

Wild Number of infections: 0 - 49 Number of sites: 0 - 2 Geographical distribution: Low Threat containment: Easy Removal: Moderate

Threat Metrics Wild: Low Damage: Medium Distribution: Medium

Damage

• Payload Trigger: n/a
• Payload: Opens a back door.
  • Large scale e-mailing: n/a
  • Deletes files: n/a
  • Modifies files: n/a
  • Degrades performance: n/a
  • Causes system instability: n/a
  • Releases confidential info: n/a
  • Compromises security settings: Lowers security settings by disabling security-related settings.

Distribution

• Subject of email: n/a
• Name of attachment: n/a
• Size of attachment: n/a
• Time stamp of attachment: n/a
• Ports: Random
• Shared drives: n/a
• Target of infection: AOL, MSN and Yahoo Instant Messenger

When W32.Loxbot.F is executed, it performs the following actions:

1. Copies itself as %System%\lockbr.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. Adds the value:
   
   "freexstyle" = "lockbr.exe"
   
   to the registry subkeys:
   
   HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
   HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\
   RunServices
   HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
   
   so that it runs every time Windows starts.
   
   
3. Modifies the value:
   
   "EnableFirewall" = "0"
   
   in the registry subkey:
   
   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SharedAccess\
   Parameters\FirewallPolicy\StandardProfile
   
   to disable and allow it to bypass the Windows Firewall.
   
   
4. Modifies the value:
   
   "system32" = "C:\WINDOWS\system32:*:Enabled:lockx"
   
   in the registry subkeys:
   
   HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\SharedAccess\Parameters
   \FirewallPolicy\StandardProfile\AuthorizedApplications\List\C:\WINDOWS
   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters
   \FirewallPolicy\StandardProfile\AuthorizedApplications\List\C:\WINDOWS
   
   to disable and allow it to bypass the Windows Firewall.
   
   
5. Drops and executes the file C:\xz.bat to disable the following services:
   
   
   • Security Center
   • Windows Update
   • Windows Firewall/Internet Connection Sharing (ICS)
     
     
6. Opens a back door and contacts the IRC server q8l0rd.linux-dude.net through a random TCP port allowing
   a remote attacker to perform any of the following actions:
   
   
   • Disconnect or reconnect to the server
   • Download and execute files
   • Generate a new random nickname
   • Update itself with a new version of the worm
     
     
7. Sends a link that contains a copy of the worm to all the online AOL, MSN and Yahoo Instant Messenger
   contacts on the compromised computer.

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

• Turn off and remove unneeded services. By default, many operating systems install auxiliary services that are not critical, such as an FTP server, telnet, and a Web server. These services are avenues of attack. If they are removed, blended threats have less avenues of attack and you have fewer services to maintain through patch updates.
• If a blended 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 (for example, all Windows-based computers should have the current Service Pack installed.). Additionally, please apply any security updates that are mentioned in this writeup, in trusted Security Bulletins, or on vendor Web sites.
• 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.
• Configure your email server to block or remove email that contains file attachments that are commonly used to spread viruses, such as .vbs, .bat, .exe, .pif and .scr files.
• Isolate infected computers quickly to prevent further compromising your organization. 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.

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 and delete all the files detected.
4. Delete any values added to the registry.
5. Restore the Windows Security Center.
6. Reenable the SharedAccess service (Windows 2000/XP only)
   

• How to disable or enable Windows Me System Restore
• How to turn off or turn on Windows XP System Restore

• 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.

1. Start your Symantec antivirus program and make sure that it is configured to scan all the files.
   • For Norton AntiVirus consumer products: Read the document: How to configure Norton AntiVirus to scan all files.
   • For Symantec AntiVirus Enterprise products: Read the document: How to verify that a Symantec Corporate antivirus product is set to scan all files.
2. Run a full system scan.
3. If any files are detected, click Delete.

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\Windows\CurrentVersion\Run
   HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\
   RunServices
   HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
   
   
5. In the right pane, delete the value:
   
   "freexstyle" = "lockbr.exe"
   
   
6. Exit the Registry Editor.
   

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.

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.

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.