W32.HLLW.Dax

SUMMARY

W32.HLLW.Dax is a worm that spreads through open shares across the network. It attempts to replicate itself to that share as the file "Ordin Popescu.exe."

It also contains a backdoor that enables a remote attacker to connect to and control the computer. By default it opens port 3256 on the compromised computer.

Protection

• Virus Definitions (LiveUpdate™ Weekly) September 18, 2002
• Virus Definitions (Intelligent Updater) September 18, 2002

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
• Modifies Files: Modifies the registry.
• Causes System Instability: The worm may drop a Trojan that will overwrite critical data with garbage.
• Compromises Security Settings: The worm contains backdoor Trojan functionality that will allow unauthorized access to an infected computer.

Distribution

• Distribution Level: Medium
• Ports: 3256
• Shared Drives: Replicates itself to open shares across the network.

TECHNICAL DETAILS

In its functionality, W32.HLLW.Dax is similar to W32.HLLW.Qaz.A. When W32.HLLW.Dax runs, it performs the following actions:

It copies itself as %system%Rundlll.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).

The worm creates the value

PowerManagement    %system%undlll.exe

in the registry key

HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun

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

The worm enumerates all the resources on a network. If it locates an unrestricted share, it attempts to replicate itself to that share as the file "Ordin Popescu.exe."

After the worm has replicated, it notifies the client side using email. The text of the email message contains the IP address of the infected computer. The backdoor payload opens port 3256 and waits for a connection. This enables a hacker to connect to and gain access to the infected computer.

The worm contains code that permits it to enumerate all fixed drives on the infected computer, and then enumerate and delete all files on those drives. Also, the worm may drop the file C:Test.com (detected by Symantec antivirus products as Trojan.Horse) and modify the C:Autoexec.bat file with a command that runs the Trojan.

Next, the worm may restart the computer; the Trojan then runs and overwrites critical data on the first physical drive with garbage. This leads to complete data corruption on the drive.

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 worm process.
3. Run a full system scan, and delete all files that are detected as W32.HLLW.Dax.
4. Reverse the change that the worm made to the registry.
5. (Windows 95/98/Me only) Remove the commands that the worm added to C:Autoexec.bat.
   

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

To update the virus definitions:
All virus definitions receive full quality assurance testing by Symantec Security Response before being posted to our servers. There are two ways to obtain the most recent virus definitions:

• Run LiveUpdate, which is the easiest way to obtain virus definitions. These virus definitions 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 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 the computer in Safe mode or end the worm 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:

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 the following names:
   • Rundlll.exe
   • Ordin Popescu.exe
6. For each of the two files that you find, click the name, and then click End Process.
7. Exit 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 configure 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.Dax or Trojan.Horse, click Delete.

To reverse the change 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 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
   
   PowerManagement    %system%undlll.exe
   
5. Exit the Registry Editor.

To remove the commands that the worm added to C:Autoexec.bat:
This is necessary only on Windows 95/98/Me-based computers.

NOTE: (For Windows Me users only) Due to the file-protection process in Windows Me, a backup copy of the file that you are about to edit exists in the C:WindowsRecent folder. Symantec recommends that you delete this file before you continue with the steps in this section. To do this using Windows Explorer, go to C:WindowsRecent, and in the right pane select the Win.ini file and delete it. It will be regenerated as a copy of the file that you are about to edit when you save your changes to that file.

1. Click Start, and click Run.
2. Type the following, and then click OK.
   
   edit c:autoexec.bat
   
   The MS-DOS Editor opens.
3. Look for these two lines:
   
   @ECHO OFF
   C: est.com
   
4. For each one that you find, select the entire line. Be sure that you do not select any other text, and then press Delete.
5. Click File, and click Save.
6. Click File, and click Exit.