W32.HLLW.Astef

SUMMARY

W32.HLLW.Astef is a worm that attempts to spread through file-sharing networks, such as KaZaA, KaZaA Lite, Grokster, Bearshare, eDonkey2000, Morpheus, Limewire, Overnet, Papigator, XoloX, Tesla, WinMX, Shareaza, Gnucleus, and ICQ as well.

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Note: Definitions dated prior to August 27, 2003 may detect this threat as Bloodhound.W32.5.

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Protection

• Virus Definitions (LiveUpdate™ Weekly) August 27, 2003
• Virus Definitions (Intelligent Updater) August 27, 2003

Threat Assessment

Wild

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

Damage

• Damage Level: Medium
• Modifies Files: Renames various programs and then copies itself as the original executable.

Distribution

• Distribution Level: Medium
• Shared Drives: Attempts to copy itself to the default shared folders of some file-sharing networks.

TECHNICAL DETAILS

When W32.HLLW.Astef runs, it does the following:

1. Renames the following files, if they exist:
   • %Windir%Calc.exe to %System%Calc.com
   • %Windir%Notepad.exe to %System%Notepad.exe
   • %Windir%sol.exe to %System%sol.com
   • %Windir%freecell.exe to %System%freecell.com
   • C:progra~1 rillian rillian.exe to C:progra~1 rillian rillian.com
   • C:progra~1msnmes~1msnmsgr.exe to C:progra~1msnmes~1msnmsgr.com
   • C:progra~1icqicq.exe to C:progra~1icqicq.com
     
     NOTES:
     • %Windir% is a variable. The worm locates the Windows installation folder (by default, this is C:Windows or C:Winnt) and copies itself to that location.
     • %System% is a variable. The worm locates the System folder and copies itself to that location. By default, this is C:WindowsSystem (Windows 95/98/Me), C:WinntSystem32 (Windows NT/2000), or C:WindowsSystem32 (Windows XP).
       
       
2. Copies itself as the following:
   • %Windir%Calc.exe
   • %Windir%Notepad.exe
   • %Windir%freecell.exe
   • %Windir%ocx32.exe
   • %Windir%sol.exe
   • %Windir%svchost.exe
   • %Windir%windll32.exe
   • %Windir%windows_critical_update.exe
   • %Windir%windowsupdate.exe
   • C:progra~1 rillian rillian.exe
   • C:progra~1msnmes~1msnmsgr.exe
   • C:progra~1icqicq.exe
     
     
3. Creates the text file, %System%Driversys.dat.
   
   
4. Adds the values:
   
   "WindowsCriticalUpdate"="%Windir%windows_critical_update.exe"
   "WIndowsUpdate"="svchost.exe"
   
   to the registry key:
   
   HKEY_CURRENT_USERSoftwareMicrosoftWindowsCurrentVersionRun
   
   
5. Adds the values:
   
   "windll"="%Windir%windll32.exe"
   "ocx32"="%Windir%ocx32.exe"
   "microsoft"="%Windir%svchost.exe"
   
   to the registry key:
   
   HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersionRun
   
   
6. Modifies the value data of the value, "DisableSharing," to 0 in the registry key:
   
   HKEY_CURRENT_USERSoftwareKazaaLocalContent
   
   
7. Modifies the value data of the value, "DisableSharing," to 0 in the registry key:
   
   HKEY_CURRENT_USERSoftwareGroksterLocalContent
   
   
8. In the registry key:
   
   HKEY_CURRENT_USERSoftwareMicrosoftWindowsCurrentVersion
   ExplorerAdvanced
   
   Modifies the values to the following:
   
   "Hidden"=0
   "ShowSuperHidden"=0
   
   
9. Attempts to copy itself to the following folders:
   
   • C:Program Fileskazaamy shared folder
   • C:Program Fileskazaa litemy shared folder
   • C:Program FilesKazaa Lite K++my shared folder
   • C:Program Fileskmdmy shared folder
   • C:Program Filesgrokstermy grokster
   • C:Program Filesearshareshared
   • C:Program Filesedonkey2000incoming
   • C:Program Filesmorpheusmy shared folder
   • C:Program Fileslimewireshared
   • C:Program Fileswinmxshared
   • C:Program FilesRapigatorShare
   • C:Program FilesXoloXDownloads
   • C:Program FilesTeslaFiles
   • C:Program FilesWinMXMy Shared Folder
   • C:Program FilesShareazaDownloads
   • C:Program FilesGnucleusDownloads
   • C:program filesICQShared Folder
   • C:program filesovernetincoming
   • C:my shared folder
   • C:My Downloads
     
     Here are some examples of the filenames that the worm copies itself as:
     
     
   • HotMail Hack.exe
   • AIM & AOL Password Hacker.exe
   • Mircosoft CD Key Generator.exe
   • PornStar3D.exe
   • Spy Toolz.exe
   • XBOX-BootDVD+Instructions.exe
   • Sony PlayStation Hack Boot Disk (No MOD Chip Needed)-Working.exe
   • simsonline(money-cheat)-WORKS.exe
   • Super Sex Games.exe

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 and delete all the files detected as W32.HLLW.Astef. Delete the file, %System%driversys.dat.
4. Delete the values that were added to the registry.
5. Rename the following files, if they exist:
   • %System%Calc.com to %Windir%Calc.exe
   • %System%Notepad.exe to %Windir%Notepad.exe
   • %System%sol.com to %Windir%sol.exe
   • %System%freecell.com to %Windir%freecell.exe
   • C:progra~1 rillian rillian.com to C:progra~1 rillian rillian.exe
   • C:progra~1msnmes~1msnmsgr.com to C:progra~1msnmes~1msnmsgr.exe
   • C:progra~1icqicq.com to C:progra~1icqicq.exe
     

For specific details on each of these steps, read the following instructions.

1. Disabling 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"

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. Updating 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).
• 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. Scanning for and deleting 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.HLLW.Astef, click Delete.
4. Useing Windows Explorer, delete the file, %System%driversys.dat.

4. Deleting the values from the registry

CAUTION: 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.

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 key:
   
   HKEY_CURRENT_USERSOFTWAREMicrosoftWindowsCurrentVersionRun
   
   
4. In the right pane, delete the values:
   
   "WindowsCriticalUpdate"="%Windir%windows_critical_update.exe"
   "WIndowsUpdate"="svchost.exe"
   
   
5. Navigate to the key:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun
   
   
6. In the right pane, delete the values:
   
   "windll"="%Windir%windll32.exe"
   "ocx32"="%Windir%ocx32.exe"
   "microsoft"="%Windir%svchost.exe"
   
   
7. Exit the Registry Editor.

5. Renaming the files
You can either use the DOS rename command if you are familiar with its usage, or use Windows Explorer to copy the following files to the locations indicated:

• %System%Calc.com to %Windir%Calc.exe
• %System%Notepad.exe to %Windir%Notepad.exe
• %System%sol.com to %Windir%sol.exe
• %System%freecell.com to %Windir%freecell.exe
• C:progra~1 rillian rillian.com to C:progra~1 rillian rillian.exe
• C:progra~1msnmes~1msnmsgr.com to C:progra~1msnmes~1msnmsgr.exe
• C:progra~1icqicq.com to C:progra~1icqicq.exe