W32.HLLW.GOP@mm

SUMMARY

W32.HLLW.GOP@mm is a mass-mailing worm that copies itself to the hard drive as C:WindowsSystemKernelsys32.exe. It also searches the network drives and copies itself to RecycledNotdelw.i.n.v.e.r.y.i.f.y.exe on any mapped drive on which it can find an operating system. Then, W32.HLLW.GOP@mm sets that particular file to run at startup by modifying the Win.ini file.

Protection

• Virus Definitions (LiveUpdate™ Weekly) December 19, 2001
• Virus Definitions (Intelligent Updater) December 15, 2001

Threat Assessment

Wild

• Wild Level: Medium
• Number of Infections: 50 - 999
• Number of Sites: 3 - 9
• Geographical Distribution: Medium
• Threat Containment: Moderate
• Removal: Moderate

Damage

• Damage Level: Low
• Payload: Mails itself to many email addresses
• Large Scale E-mailing: Sends itself to email addresses found on the computer

Distribution

• Distribution Level: High
• Subject of Email: Random
• Name of Attachment: Random name with double extension
• Size of Attachment: Approximately 63KB
• Shared Drives: Searches for shared system drives and copies itself to the Recycled folder

TECHNICAL DETAILS

When W32.HLLW.GOP@mm is executed, it does the following:

1. Copies itself as C:WindowsSystemKernelsys32.exe. It also drops the file, IMEKernel32.sys, in which it stores stolen passwords.
   
2. Adds the value:
   
   IMEKernel32   C:WindowsSystemKernelsys32.exe
   
   to the registry key:
   
   HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersionRun
   
3. Performs its mass-mailing routine. Most of the time, the email message that the worm sends will contain a subject and message in Chinese. The attachment will be a .bmp, .rtf, .doc, .txt, .gif, .jpeg, or .jpg file, which it has taken from your computer.
   
   To the original file name, it adds a second file extension, either .exe or .lnk. For example, if the original file name is Birthday pic.bmp, the name of the attachment will be Birthday pic.bmp.exe or Birthday pic.bmp.lnk.
   
4. Searches for the email addresses in the .htm and .html files, as well as in many different email mailbox files. After gathering all the email addresses that the worm can find, it uses its own SMTP engine to send an email message that can be executed (on unpatched systems), when the recipient reads it.
   
   NOTE: The worm takes advantage of the IFRAME vulnerability that allows Microsoft Outlook to automatically execute the attachments. Information on this vulnerability can be found at: http://www.microsoft.com/windows/ie/downloads/critical/q290108/default.asp.
   
5. Inventories all the resources in the network. The worm also attempts to copy itself to all the shared drives or folders. Because the worm does not properly handle the network resource types, it may flood shared printer resources, which causes them to print garbage or disrupt their normal functionality.
   
6. Searches the network drives and copies itself to RecycledNotdelw.i.n.v.e.r.y.i.f.y.exe on any mapped drive on which it can find an operating system. Then, it sets that particular file to run at startup by modifying the Win.ini file.

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

To remove this worm, delete the files detected as W32.HLLW.GOP@mm, and remove the value that it added to the registry.

Removing the worm

1. Run LiveUpdate to make sure that you have the most recent virus definitions.
2. Start Norton AntiVirus (NAV) and make sure that NAV is configured to scan all the files. For instructions on how to do this, read the document, "How to configure Norton AntiVirus to scan all files."
3. Run a full system scan.
4. Delete all the files detected as W32.HLLW.GOP@mm.
5. Perform a file search for IMEKernel32.sys and delete the file.

Editing the registry

CAUTION: We strongly recommend 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 back up the Windows registry," for instructions.

1. Click Start, and the click Run. (The Run dialog box appears.)
2. Type regedit, and then click OK. (The Registry Editor opens.)
3. Navigate to the following key:
   
   HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersionRun
   
4. In the right pane, delete the following value:
   
   IMEKernel32   C:WindowsSystemKernelsys32.exe
   
5. Click Registry, and click Exit.