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Discovered: December 13, 2001
Updated: February 13, 2007 11:37:55 AM
Also Known As: W32/GOP@MM [McAfee], W32/Gop-A [Sophos], W32/Gop-C [Sophos], Troj/Gop [Sophos], WORM_GOP.A [Trend], WORM_GOP.B [Trend], WORM_GOP.E [Trend], Win32.PSW.Gop.196.2 [CA], Win32.PSW.Gop.196.3 [CA], I-Worm.GOPworm.153 [KAV], I-Worm.GOPworm.153.b [KAV], I-Worm.GOPworm.1963 [KAV], I-Worm.GOPworm.196 [KAV], Trojan.PSW.GOPtrojan.196 [KAV]
Type: Worm
Systems Affected: Windows
CVE References: CVE-2001-0154

W32.HLLW.GOP@mm is a mass-mailing worm that copies itself to the hard drive as C:\Windows\System\Kernelsys32.exe. It also searches the network drives and copies itself to \Recycled\Notdelw.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.

Antivirus Protection Dates

  • Initial Rapid Release version December 15, 2001
  • Latest Rapid Release version March 23, 2017 revision 037
  • Initial Daily Certified version December 15, 2001
  • Latest Daily Certified version March 23, 2017 revision 041
  • Initial Weekly Certified release date December 19, 2001

Click here for a more detailed description of Rapid Release and Daily Certified virus definitions.

Technical Description

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

  1. Copies itself as C:\Windows\System\Kernelsys32.exe. It also drops the file, IMEKernel32.sys, in which it stores stolen passwords.
  2. Adds the value:

    IMEKernel32   C:\Windows\System\Kernelsys32.exe

    to the registry key:

  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 \Recycled\Notdelw.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.


Symantec Security Response encourages all users and administrators to adhere to the following basic security "best practices":

  • Use a firewall to block all incoming connections from the Internet to services that should not be publicly available. By default, you should deny all incoming connections and only allow services you explicitly want to offer to the outside world.
  • 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.
  • Ensure that programs and users of the computer use the lowest level of privileges necessary to complete a task. When prompted for a root or UAC password, ensure that the program asking for administration-level access is a legitimate application.
  • Disable AutoPlay to prevent the automatic launching of executable files on network and removable drives, and disconnect the drives when not required. If write access is not required, enable read-only mode if the option is available.
  • Turn off file sharing if not needed. If file sharing is required, use ACLs and password protection to limit access. Disable anonymous access to shared folders. Grant access only to user accounts with strong passwords to folders that must be shared.
  • Turn off and remove unnecessary services. By default, many operating systems install auxiliary services that are not critical. These services are avenues of attack. If they are removed, threats have less avenues of attack.
  • If a 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.
  • Configure your email server to block or remove email that contains file attachments that are commonly used to spread threats, such as .vbs, .bat, .exe, .pif and .scr files.
  • Isolate compromised computers quickly to prevent threats from spreading further. 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.
  • If Bluetooth is not required for mobile devices, it should be turned off. If you require its use, ensure that the device's visibility is set to "Hidden" so that it cannot be scanned by other Bluetooth devices. If device pairing must be used, ensure that all devices are set to "Unauthorized", requiring authorization for each connection request. Do not accept applications that are unsigned or sent from unknown sources.
  • For further information on the terms used in this document, please refer to the Security Response glossary.


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:

  4. In the right pane, delete the following value:

    IMEKernel32   C:\Windows\System\Kernelsys32.exe
  5. Click Registry, and click Exit.

Writeup By: Douglas Knowles