Discovered: August 21, 2003
Updated: February 13, 2007 12:08:54 PM
Also Known As: Backdoor.Lorac, Worm.Win32.Eyeveg.a [AVP], W32/Eyeveg.worm [McAfee]
Type: Worm
Systems Affected: Windows

W32.Lorac is a network aware worm that allows remote control of an infected system, via HTTP.

This worm has been distributed as an email attachment named An HTML file, which contains the worm, exists inside the zip file. The worm takes advantage of a vulnerability described in MS03-14 , which allows for the execution of a MIME-encoded program inside an HTML file.

NOTE: Definitions dated prior to Octomer 9, 2003 may detect this as Backdoor.Lorac.

Antivirus Protection Dates

  • Initial Rapid Release version August 22, 2003
  • Latest Rapid Release version July 27, 2018 revision 005
  • Initial Daily Certified version August 22, 2003
  • Latest Daily Certified version July 27, 2018 revision 008
  • Initial Weekly Certified release date August 27, 2003

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

Writeup By: Heather Shannon

Discovered: August 21, 2003
Updated: February 13, 2007 12:08:54 PM
Also Known As: Backdoor.Lorac, Worm.Win32.Eyeveg.a [AVP], W32/Eyeveg.worm [McAfee]
Type: Worm
Systems Affected: Windows

When W32.Lorac is executed, it does the following:

  1. Generates a filename of the form abcdef.exe. The actual filename is a function of the volume serial number, so the name will be different for every computer.

  2. Copies itself to the System folder using the generated filename.

  3. Adds the value:

    "<four random characters>"= "%Sysdir%\abcdef.exe"

    to the registry key:


    so that the worm runs when you start Windows.

  4. Queries the registry key:

    Explorer\Shell Folders\Common Startup

    and copies itself to this folder as Explorer.exe.
  5. Enumerates all network resources to locate remote machines.
  6. Queries the registry key:

    Explorer\Shell Folders\Common Startup

    on the remote machine to locate the Startup folder.
  7. Copies itself to this folder as Explorer.exe.
  8. Uses an internal SMTP client to send email notification to a certain address.

  9. Periodically downloads a file from a certain Web site. This file contains commands that control the execution of the worm. Depending on the commands that the worm receives, the worm may:
    • Retrieve system information
    • Manipulate files (copy, move, create, or delete)
    • Upload and download files
    • Execute arbitrary programs
    All communication between the backdoor and the remote system takes place via HTTP transactions. The resulting network activity will resemble normal HTTP traffic.


    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.

    Writeup By: Heather Shannon

    Discovered: August 21, 2003
    Updated: February 13, 2007 12:08:54 PM
    Also Known As: Backdoor.Lorac, Worm.Win32.Eyeveg.a [AVP], W32/Eyeveg.worm [McAfee]
    Type: Worm
    Systems Affected: Windows

    The following instructions pertain to all current and recent Symantec antivirus products, including the Symantec AntiVirus and Norton AntiVirus product lines.

    1. Disable System Restore (Windows Me/XP).
    2. Update the virus definitions.
    3. Run a full system scan and delete all the files detected as W32.Lorac.
    4. Delete the value that was added to the registry.
    For specific details on each of these steps, read the following instructions.

    1. Disabling System Restore (Windows Me/XP)
    If you are running Windows Me or Windows XP, we recommend that you temporarily turn off System Restore. Windows Me/XP uses this feature, which is enabled by default, to restore the files on your computer in case they become damaged. If a virus, worm, or Trojan infects a computer, System Restore may back up the virus, worm, or Trojan on the computer.

    Windows prevents outside programs, including antivirus programs, from modifying System Restore. Therefore, antivirus programs or tools cannot remove threats in the System Restore folder. As a result, System Restore has the potential of restoring an infected file on your computer, even after you have cleaned the infected files from all the other locations.

    Also, a virus scan may detect a threat in the System Restore folder even though you have removed the threat.

    For instructions on how to turn off System Restore, read your Windows documentation, or one of the following articles:
    For additional information, and an alternative to disabling Windows Me System Restore, see the Microsoft Knowledge Base article, "Antivirus Tools Cannot Clean Infected Files in the _Restore Folder ," Article ID: Q263455.

    2. 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 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).
    • 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).

      The Intelligent Updater virus definitions are available: Read "How to update virus definition files using the Intelligent Updater" for detailed instructions.

    3. Scanning for and deleting the infected files
    1. Start your Symantec antivirus program and make sure that it is configured to scan all the files.
    2. Run a full system scan.
    3. If any files are detected as infected with W32.Lorac, note the filename, and then click Delete.

    NOTE: If your Symantec antivirus product reports that it cannot delete an infected file, shut down the computer, turn off the power, and wait 30 seconds. Restart the computer in Safe mode (Windows 95/98/Me/2000/XP) or VGA mode (Windows NT 4), and then run the scan again.

    For instructions on how to restart in Safe mode, read the document, "How to start the computer in Safe Mode ."

    4. Deleting the value from the registry

    CAUTION : Symantec strongly recommends 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 make a backup of the Windows registry ," for instructions.
    1. Click Start, and then click Run. (The Run dialog box appears.)
    2. Type regedit

      Then click OK. (The Registry Editor opens.)

    3. Navigate to the key:


    4. In the right pane, delete the value that refers to the worm file (noted earlier). This value has the form:

      "<four random characters>"="%Sysdir%\<filename>.exe"

    5. Exit the Registry Editor.

    Writeup By: Heather Shannon