W32.Yautoit

SUMMARY

W32.Yautoit is a worm that spreads through Yahoo! Instant Messenger.

Protection

• Virus Definitions (LiveUpdate™ Daily) September 19, 2006
• Virus Definitions (LiveUpdate™ Weekly) September 20, 2006
• Virus Definitions (Intelligent Updater) September 19, 2006
• Virus Definitions (LiveUpdate™ Plus) September 19, 2006

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: Low
• Payload: Spreads through Yahoo! Instant Messenger.

Distribution

• Distribution Level: Low

TECHNICAL DETAILS

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

1. Downloads a file from the following location:
   
   [http://]www.sukien.org/tamdiep/Download/A9[REMOVED]
   
   
2. Saves the downloaded file as the following file:
   
   %Windir% askmng.exe
   
   Note: %Windir% is a variable that refers to the Windows installation folder. By default, this is C:Windows (Windows 95/98/Me/XP) or C:Winnt (Windows NT/2000).
   
   
3. Adds the value:
   
   "Task Manager" = "%Windir% askmng.exe"
   
   to the registry subkey:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun
   
   so that it runs every time Windows starts.
   
   
4. Modifies the value:
   
   "Homepage" = "1"
   
   in the registry subkey:
   
   HKEY_CURRENT_USERSoftwarePoliciesMicrosoftInternet ExplorerControl Panel
   
   to disable the manual modification of the Internet Explorer home page.
   
   
5. Modifies the values:
   
   "DisableTaskMgr" = "1"
   "DisableRegistryTools" = "1"
   
   in the registry subkey:
   
   HKEY_CURRENT_USERSoftwareMicrosoftWindowsCurrentVersionPoliciesSystem
   
   to disable the Task Manager and the Registry Editor.
   
   
6. Modifies the value:
   
   "Start Page" = "www.sukien.org"
   
   in the registry subkey:
   
   HKEY_CURRENT_USERSoftwareMicrosoftInternet ExplorerMain
   
   to change the Internet Explorer home page.
   
   
7. Modifies the value:
   
   "content url" = "www.sukien.org"
   
   in the registry subkeys:
   
   HKEY_CURRENT_USERSoftwareYahoopagerViewYMSGR_buzz
   HKEY_CURRENT_USERSoftwareYahoopagerViewYMSGR_Launchcast
   
   to change the settings of Yahoo! Instant Messenger.
   
   
8. Modifies the value:
   
   "Window Title" = "www.sukien.org :: Another Version of www.sukien.org :: Chut gi de nho..."
   
   in the registry subkey:
   
   HKEY_CURRENT_USERSoftwareMicrosoftInternet ExplorerMain
   
   to change the title of the Internet Explorer.
   
   
9. Sends the following messages through Yahoo! Instant Messenger:
   
   
   • "Vui gi ma vui the! Dau ca bung roi ne... [http://]www.sukien.org/lo[REMOVED]"
   • "Trui, ngo nghinh qua a... Vo coi thu nao [http://]www.sukien.org/lo[REMOVED]"
   • "Vui kinh khung! Ghe qua day ti xiu nha ban [http://]www.sukien.org/lo[REMOVED]"
   • "Chao mung cac ban den voi Dao Khuc Community [http://]www.sukien.org/lo[REMOVED]"
   • "Moi phat hien ra cai nay ne, cuc hay luon nha [http://]www.sukien.org/lo[REMOVED]"
   • "Kinh di qua di mat... Toan la ma trong nay ne [http://]www.sukien.org/lo[REMOVED]"
   • "Gom gi ma gom the... Vao day ma xem gom co nao [http://]www.sukien.org/lo[REMOVED]"
   • "Cai gi the nhi? Thang ban moi quang cao cai nay [http://]www.sukien.org/lo[REMOVED]"
   • "Bo oi! Co biet gi chua ha? Cai nay hay lam a nha [http://]www.sukien.org/lo[REMOVED]"
   • "Hey! Dang lam gi vay? Bo ti thoi gian vao day nha [http://]www.sukien.org/lo[REMOVED]"

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. Run a full system scan.
4. Delete any values 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

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.
   • 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, 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_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun
   
   
5. In the right pane, delete the value:
   
   "Task Manager" = "%Windir% askmng.exe"
   
   
6. Navigate to the subkey:
   
   HKEY_CURRENT_USERSoftwarePoliciesMicrosoftInternet ExplorerControl Panel
   
   
7. In the right pane, reset the value to the default value:
   
   "Homepage" = "1"
   
   
8. Navigate to the subkey:
   
   HKEY_CURRENT_USERSoftwareMicrosoftWindowsCurrentVersionPoliciesSystem
   
   
9. In the right pane, reset the values to the default values:
   
   "DisableTaskMgr" = "1"
   "DisableRegistryTools" = "1"
   
   
10. Navigate to the subkey:
    
    HKEY_CURRENT_USERSoftwareMicrosoftInternet ExplorerMain
    
    
11. In the right pane, reset the value to the default value:
    
    "Start Page" = "www.sukien.org"
    
    
12. Navigate to the subkeys:
    
    HKEY_CURRENT_USERSoftwareYahoopagerViewYMSGR_buzz
    HKEY_CURRENT_USERSoftwareYahoopagerViewYMSGR_Launchcast
    
    
13. In the right pane, reset the value to the default value:
    
    "content url" = "www.sukien.org"
    
    
14. Navigate to the subkey:
    
    HKEY_CURRENT_USERSoftwareMicrosoftInternet ExplorerMain
    
    
15. In the right pane, reset the value to the default value:
    
    "Window Title" = "www.sukien.org :: Another Version of www.sukien.org :: Chut gi de nho..."
    
    
16. Exit the Registry Editor.