W32.HLLW.Apart

SUMMARY

W32.HLLW.Apart is a worm with the backdoor capabilities that spreads through open shares. W32.HLLW.Apart is a Delphi application, packed with UPX v0.76.1-1.22.

Protection

• Virus Definitions (LiveUpdate™ Weekly) September 4, 2002
• Virus Definitions (Intelligent Updater) August 30, 2002

TECHNICAL DETAILS

The functionality of W32.HLLW.Apart derives from W32.HLLW.Acebo. When W32.HLLW.Apart runs, it performs the following actions:

It copies itself as the file %system%Kernel32.dll<appended 0xA0 character>.

NOTES:

• This file, which has an 0xA0 character appended to the .dll file extension, should not be confused with the legitimate Windows system file Kernel32.dll. In certain language versions of Windows this character is displayed as space.
• %system% is a variable. The worm locates the WindowsSystem folder (by default, this is C:WindowsSystem or C:WinntSystem32) and uses it as a destination folder.

The worm creates the value

Kernel    %system%Kernel32.dll<appended 0xA0 character>.

in the registry key

HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun

so that the worm starts when you start or restart Windows.

NOTE: To enable itself to run, the worm associates the extension .dll (with an appended 0xA0 character) with an executable file. It creates the registry key

HKEY_LOCAL_MACHINESOFTWAREClasses.dll <with an appended 0xA0 character>

and places the following string in its default value of

exefile

The worm creates the "Apartheid v.2.0" mutex. This mutex allows only one instance of the worm to run in memory.

The worm enumerates all of the resources on a network. If it locates any shares of drive C (including administrator shares), it maps the drive letter W to that share and attempts to copy itself as

W:WINDOWSStart MenuProgramsStartUpWindows.exe

Then, the worm disconnects (unmaps) the redirected local device W. This results in propagation of the worm into the StartUp folders of the unrestricted network shares.

W32.HLLW.Apart connects to an IRC server using port 6667, joins a specific channel, and sends a private message to notify the hacker. It relies on an officially undocumented function, WNetEnumCachedPasswords, which exists only in versions of Mpr.dll that were written for Windows 95/98/Me. It uses this function to obtain an access to the password cache that is stored on the local computer. The cached passwords include modem and dial-up passwords, URL passwords, share passwords, and others.

After the connection with the hacker is established, the worm performs its backdoor functions:

• Deliver system and network information to the hacker, including login names and cached network passwords
• Perform Denial of Service (DoS) attacks
• Scan the given ranges of IP addresses
• Connect to the installed capture drivers, make a single-frame data capture, and deliver the captured data to the hacker.
• Manage self-installation
• Download and execute files

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

NOTE: These instructions are for all current and recent Symantec antivirus products, including the Symantec AntiVirus and Norton AntiVirus product lines.

1. Update the virus definitions.
2. Do one of the following:
   • Windows 95/98/Me: Restart the computer in Safe mode.
   • Windows NT/2000/XP: Stop the Kernel32.dll process that is running.
3. Run a full system scan, and delete all files that are detected as W32.HLLW.Apart.
4. Reverse the changes that the worm made to the registry.
   

For details on how to do this, read the following instructions.

To update the virus definitions:
There are two ways to do this:

• Run LiveUpdate, which is the easiest way to obtain virus definitions. These virus definitions have undergone full quality assurance testing by Symantec Security Response and are posted to the LiveUpdate servers one time each week (usually Wednesdays) unless there is a major virus outbreak. To determine whether definitions for this threat are available by LiveUpdate, look at the Virus Definitions (LiveUpdate) line at the top of this write-up.
• Download the definitions using the Intelligent Updater. Intelligent Updater virus definitions have undergone full quality assurance testing by Symantec Security Response. They are posted on U.S. business days (Monday through Friday). They must be downloaded from the Symantec Security Response Web site and installed manually. To determine whether definitions for this threat are available by the Intelligent Updater, look at the Virus Definitions (Intelligent Updater) line at the top of this write-up.
  
  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.

To restart in Safe mode or stop the process:
Windows 95/98/Me
Restart the computer in Safe mode. All Windows 32-bit operating systems, except for Windows NT, can be restarted in Safe mode. For instructions on how to do this, read the document How to start the computer in Safe Mode.

Windows NT/2000/XP
To stop the Kernel32.dll process:

1. Press Ctrl+Alt+Delete one time.
2. Click Task Manager.
3. Click the Processes tab.
4. Double-click the Image Name column header to sort the processes alphabetically.
5. Scroll through the list, and look for Kernel32.dll.
6. If you find the file, click it, and then click End Process.
7. Close the Task Manager.
   

To scan for and delete the infected files:

1. Start your Symantec antivirus program, and make sure that it is configured to scan all files.
   • Norton AntiVirus consumer products: Read the document How to confiegure Norton AntiVirus to scan all files.
   • Symantec enterprise antivirus products: Read the document How to verify 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.Apart, click Delete.

To reverse the changes that the worm 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 only the keys that are specified. Read the document How to make a backup of the Windows registry for instructions.

1. Click Start, and click Run. The Run dialog box appears.
2. Type regedit and then click OK. The Registry Editor opens.
3. Navigate to the key
   
   HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersionRun
   
4. In the right pane, delete the value
   
   Kernel    %system%Kernel32.dll<appended 0xA0 character>.
   
5. Exit the Registry Editor.