W32.HLLC.Hoa

SUMMARY

W32.HLLC.Hoa is a companion virus that renames all the .exe files that are in the same folder as the virus, so that the files have a .dll extension. Then, it makes copies of itself as the original file names.

W32.HLLC.Hoa also overwrites all the .doc files that are in the same folder as the virus. The overwritten .doc files become 162 byte text files.

Protection

• Virus Definitions (LiveUpdate™ Weekly) January 9, 2003
• Virus Definitions (Intelligent Updater) January 8, 2003

TECHNICAL DETAILS

When W32.HLLC.Hoa runs, it does the following:

1. Copies itself as C:\%Windir%Hllchai.exe.
   
   NOTE: %Windir% is a variable. The virus locates the Windows installation folder and copies itself to that location. By default, this is C:Windows or C:Winnt.
   
2. Inserts the following line into the C:Autoexec.bat file:
   
   set HoiVirus=Active
   
3. Overwrites the C:Winstart.bat file with the following text:
   
   @echo off
   echo WARNING: Your computer is infected with HOI Virus
   echo If you will go on with running windows
   echo you can lose your programms and documents
   echo it is recomended now to boot to DOS and run DrWeb
   pause
   
4. Renames all the .exe files in the same folder as the virus, so that the files have a .dll extension.
5. Makes copies of itself as the original file names.
6. Overwrites all the .doc files in the same folder as the virus with the following text:
   
   All document data lost. It was erased by Hoi Virus
   Gashish Marihuanov recomends installing SpiderGuard.
   Respect to Magistr author. DrWeb Is The BEST AntiVirus

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

These 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. Restart the computer in Safe mode.
3. Run a full system scan.
   • If a .exe file is detected as W32.HLLC.Hoa, delete it, and then rename the .dll file, with the same name as the deleted .exe file, to the .exe extension.
   • Manually delete all the overwritten .doc files. Restore the .doc files from the backup copies, if necessary.
   • Restore the C:Winstart.bat from a known clean copy, if necessary.
4. Remove the line that the virus added to the C:Autoexec.bat file.
   

For specific details on each of these procedures, 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 the 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), in the "Protection" section, at the top of this writeup.
• 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), in the "Protection" section, at the top of this writeup.
  
  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. Restarting the computer in Safe mode
All the Windows 32-bit operating systems, except 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."


3. Scanning for and deleting 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.HLLC.Hoa, write down the location and file names, and then click Delete.
4. Using Windows Explorer, locate each of the files whose names you wrote down in the previous step. The file names will be the same, but the files will have the .dll extension.
5. For each one that you find, right-click the file, and then click Rename. Change the extension from .dll to .exe. Click OK to any "warninm" message that appears.
6. If the virus overwrote any .doc files, replace them from a clean backup.
7. C:Winstart.bat does not always exist on every system. If your computer uses it, and it was overwritten, delete it and replace it from a clean backup copy.

4. Removing the line that was added to the Autoexec.bat file (Windows 95/98/Me only)

Note for Windows Me users only: Due to the file-protection process in Windows Me, a backup copy of Win.ini 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. The Win.ini file will be recreated in C:WindowsRecent when you save your changes to Win.ini in C:Windows.

1. Click Start, and then click Run.
2. Type the following:
   
   edit c:autoexec.bat
   
   and then click OK.
   
   (The MS-DOS Editor opens.)
   
3. Locate and delete the line:
   
   set HoiVirus=Active
   
4. Click File, and then click Save.
5. Click File, and then click Exit.