W32.Gaobot.AUS

SUMMARY

W32.Gaobot.AUS is a repacked variant of W32.Gaobot.SN. The worm spreads through open network shares and through backdoors that the Mydoom family of worms open. It allows attackers to access an infected computer using a predetermined IRC channel.

Protection

• Initial Rapid Release version June 29, 2004
• Latest Rapid Release version June 29, 2004
• Initial Daily Certified version June 29, 2004
• Latest Daily Certified version June 29, 2004
• Initial Weekly Certified release date June 30, 2004

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: Medium

TECHNICAL DETAILS

When W32.Gaobot.AUS is executed, it performs the following actions:

1. Copies itself to one of the following locations:
   
   • %System%\Msnss.exe
   • %System%\Msgfix.exe
     
     

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     Note: %System% is a variable. The worm locates the System folder and copies itself to that location. By default, this is C:\Windows\System (Windows 95/98/Me), C:\Winnt\System32 (Windows NT/2000), or C:\Windows\System32 (Windows XP).

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2. Adds one of the values:
   
   "Configuration Loader"="msnss.exe"
   "Configuration Loader"="msgfix.exe"
   
   to the registry keys:
   
   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 the worm executes every time Windows starts.
   
   
3. Connects to a remote IRC server and listens for commands from the remote attacker, including the following:
   
   • Download and execute files
   • Scan the network
   • List, stop, and start processes
   • Control the file system (Delete, create, and list files)
   • Launch Denial of Service (DoS) attacks
   • Perform port redirection
   • Steal system information and email it to the attacker
     
     
4. Scans for other computers on the network, attempting to connect to shared resources using a list of usernames and passwords. If successful, it attempts to copy itself to the remote computer as the following files:
   
   • IPC$\msgfix.exe
   • D$\msgfix.exe
   • print$\msgfix.exe
   • c$\msgfix.exe
   • Admin$\msgfix.exe
   • c$\windows\system32\msgfix.exe
   • c$\winnt\system32\msgfix.exe
   • Admin$\system32\msgfix.exe
     
     
5. Scans for computers that have been infected by Mydoom variants. If it finds any, it uses the backdoor installed by Mydoom to copy itself onto the computer as Msgfix.exe.
   
   
6. Steals CD keys of the following computer games:
   
   • Command & Conquer Generals
   • FIFA 2003
   • Need For Speed Hot Pursuit 2
   • Soldier of Fortune II - Double Helix
   • Neverwinter
   • Rainbow Six III RavenShield
   • Battlefield 1942 Road To Rome
   • Project IGI 2
   • Counter-Strike
   • Unreal Tournament 2003
   • Half-Life

Recommendations

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.

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. Restart the computer in Safe mode or VGA mode.
4. Run a full system scan and delete all the files detected as W32.Gaobot.AUS.
5. Delete the value that was added to the registry.
   

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:

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

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Note: When you are completely finished with the removal procedure and are satisfied that the threat has been removed, re-enable System Restore by following the instructions in the aforementioned documents.

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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: These virus definitions are posted to the LiveUpdate servers once each week (usually on Wednesdays), unless there is a major virus outbreak. To determine whether definitions for this threat are available by LiveUpdate, refer to the Virus Definitions (LiveUpdate).
  
  

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  Note: If this Trojan is running, you may not be able to run LiveUpdate. If you cannot, download the definitions using the Intelligent Updater (see the next bulleted item).

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• Downloading the definitions using the Intelligent Updater: The Intelligent Updater virus definitions are posted on U.S. business days (Monday through Friday). 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 the Virus Definitions (Intelligent Updater).
  
  The Intelligent Updater virus definitions are available: Read "How to update virus definition files using the Intelligent Updater" for detailed instructions.

3. To restart the computer in Safe mode or VGA mode
Shut down the computer and turn off the power. Wait for at least 30 seconds, and then restart the computer in Safe mode or VGA mode.

• For Windows 95, 98, Me, 2000, or XP users, restart the computer in Safe mode. For instructions, read the document, "How to start the computer in Safe Mode."
• For Windows NT 4 users, restart the computer in VGA mode.

4. To scan for and delete the infected files

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 as infected with W32.Gaobot.AUS, write down the location and file name, and then click Delete.

5. To delete the value from the registry

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WARNING: 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 keys only. Read the document, "How to make a backup of the Windows registry," for instructions.

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1. Click Start, and then click Run. (The Run dialog box appears.)
2. Type regedit
   
   Then click OK. (The Registry Editor opens.)
   
   
3. Navigate to the keys:
   
   HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
   HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\RunServices
   HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
   
   
4. In the right pane, delete the values, if present:
   
   "Configuration Loader"="msnss.exe"
   "Configuration Loader"="msgfix.exe"
   
   
5. Exit the Registry Editor.
   
   
6. Restart the computer in Normal mode. For instructions, read the section on returning to Normal mode in the document, "How to start the computer in Safe Mode."