W32.HLLW.Kullan

SUMMARY

W32.HLLW.Kullan is a worm that has backdoor capabilities. It spreads across networks, by copying itself to the Start Menu of computers, which an infected computer can access. The most common reason for this access is an unprotected shared resource.

Some of the backdoor capabilities include retrieving information related to the computer and operating system type, logging of keystrokes, and examining email.

Protection

• Virus Definitions (LiveUpdate™ Weekly) April 30, 2003
• Virus Definitions (Intelligent Updater) April 25, 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
• Releases Confidential Info: Backdoor capabilities can log keystrokes and examine e-mail
• Compromises Security Settings: Allows unauthorized remote access to an infected computer.

Distribution

• Distribution Level: Medium
• Shared Drives: Copies itself to the Start menu on shared resources.

TECHNICAL DETAILS

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

1. Copies itself as %System%Services.exe.
   
   NOTE: %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. Uses the "net view" command to copy itself to the Start Menu of accessible computers. This worm copies itself as <computer name>.exe, where <computer name> is the name of the target computer.
   
   
3. Adds a value to the following registry keys:
   
   HKEY_CURRENT_USERSoftwareMicrosoftWindows NTCurrentVersion
   Windowsload
   HKEY_CURRENT_USERSoftwareMicrosoftWindows NTCurrentVersion
   Windowsun
   HKEY_CURRENT_USERSoftwareMicrosoftWindowsCurrentVersionRun
   HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersionRun
   
   so that W32.HLLW.Kullan runs when you start Windows.
   
   
4. Modifies the value: Shell
   
   of the following registry keys:
   
   HKEY_CURRENT_USERSoftwareMicrosoftWindows NTCurrentVersionWinlogon
   HKEY_LOCAL_MACHINESoftwareMicrosoftWindows NTCurrentVersionWinlogon
   
   so that W32.HLLW.Kullan runs when you start Windows.
   
   
5. Modifies the Win.ini and System.ini in an attempt to execute the worm when you start Windows.

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

Once this type of threat attacks a computer, it is difficult to determine what else the computer has been exposed to.

In most cases, changes—other than those made by this threat—will not have occurred. However, a hacker may have been able to use the threat to access the computer to make changes to it.

Unless you can be absolutely sure that malicious activity has not been performed on the computer, we recommend completely re-installing the operating system.

If you are on a network or have a full-time connection to the Internet, disconnect the computer from the network and the Internet. Disable or password-protect file sharing before reconnecting the computers to the network or to the Internet. Because this worm spreads by using shared folders on networked computers, to ensure that the worm does not re-infect the computer after it has been removed, Symantec suggests sharing with read only access or using password protection. For instructions, see your Windows documentation or the document, "How to configure shared Windows folders for maximum network protection."

IMPORTANT: Do not skip this step. Disconnect from the network before attempting to remove this worm.

The following instructions pertain to all current and recent Symantec antivirus products, including the Symantec AntiVirus and Norton AntiVirus product lines.

1. Update the virus definitions.
2. Run a full system scan and delete all the files detected as W32.HLLW.Kullan.
3. Reverse the changes that were made to the registry.
4. Reverse the changes that were made to the Win.ini and System.ini files (Windows 95/98/Me).
   

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

1. 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 here. For detailed instructions on how to download and install the Intelligent Updater virus definitions from the Symantec Security Response Web site, click here.

2. 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.Kullan, write down the filenames, and then click Delete.

3. Reversing the changes that were made to the registry

CAUTION: Symantec strongly recommends that you back up the registry before you make 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 keys:
   
   HKEY_CURRENT_USERSoftwareMicrosoftWindows NTCurrentVersion
   WindowsLoad
   HKEY_CURRENT_USERSoftwareMicrosoftWindows NTCurrentVersion
   WindowsRun
   HKEY_CURRENT_USERSoftwareMicrosoftWindowsCurrentVersionRun
   HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersionRun
   
   
   
4. For each one, in the right pane, delete any values that refer to the files detected as W32.HLLW.Kullan.
   
   
5. Navigate to the keys:
   
   HKEY_CURRENT_USERSoftwareMicrosoftWindows NTCurrentVersionWinlogon
   HKEY_LOCAL_MACHINESoftwareMicrosoftWindows NTCurrentVersionWinlogon
   
   
6. For each one, in the right pane, look for the value:
   
   "shell"="Explorer.exe <file name>.exe
   
   where <file name> refers to a file detected as W32.HLLW.Kullan.
   
   
7. If this data exists, delete everything to the right of Explorer.exe.
   
   When you are done, it should look like:
   
   Explorer.exe
   
   
8. Exit the Registry Editor.

4. Editing Win.ini and System.ini
If you are running Windows 95/98/Me, follow these steps:

1. The function you perform depends on your operating system:
   • Windows 95/98: Go to step b.
   • Windows Me: If you are running Windows Me, the Windows Me file-protection process may have made a backup copy of the Win.ini file that you need to edit. If this backup copy exists, it will be in the C:WindowsRecent folder. Symantec recommends that you delete this file before continuing with the steps in this section. To do this:
     1. Start Windows Explorer.
     2. Browse to and select the C:WindowsRecent folder.
     3. In the right pane, select the Win.ini file and delete it. The Win.ini file will be regenerated when you save your changes to it in step f.
        
        
        
2. Click Start, and then click Run.
   
   
3. Type the following, and then click OK.
   
   edit c:windowswin.ini
   
   (The MS-DOS Editor opens.)
   
   NOTE: If Windows is installed in a different location, make the appropriate path substitution.
   
   
4. Look for a line similar to:
   
   load = Explorer.exe <file name>.exe
   
   or:
   
   run = Explorer.exe <file name>.exe
   
   
5. If either line exists, delete the entire line.
   
   
6. Click File, and then click Save.
   
   
7. Click File, and then click Exit.
   
   
8. Click Start, and then click Run.
   
   
9. Type the following, and then click OK.
   
   edit c:windowssystem.ini
   
   (The MS-DOS Editor opens.)
   
   NOTE: If Windows is installed in a different location, make the appropriate path substitution.
   
   
10. In the [boot] section, look for a line similar to:
    
    shell = Explorer.exe <file name>.exe
    
    
11. If this line exists, delete everything to the right of Explorer.exe.
    
    When you are done, it should look like:
    
    shell = Explorer.exe
    
    
12. Click File, and then click Save.
    
    
13. Click File, and then click Exit.