Discovered: August 01, 2003
Updated: February 13, 2007 12:04:22 PM
Also Known As: WORM_MIMAIL.A [Trend], W32/Mimail@MM [McAfee], Win32.Mimail.A [CA], W32/Mimail-A [Sophos], I-Worm.Mimail [Kaspersky]
Type: Worm
Systems Affected: Windows
CVE References: CAN-2002-0980 CAN-2002-0077

W32.Mimail.A@mm is a worm that spreads by email and steals information from a user's machine.

The email has the following characteristics:

Subject: your account [random string]

  • The threat captures information from certain windows on a user's desktop and emails it to specific mail addresses.
  • This threat takes advantage of known vulnerabilities: MS02-15 and MS03-14. A Microsoft patch is located at:
  • We encourage system administrators to apply the Microsoft patch to prevent infection by this worm.
  • The worm is packed with UPX.
  • Virus definitions with a version number of 50801r, also known as August 1, 2003 rev 18, or greater will detect this threat.

Antivirus Protection Dates

  • Initial Rapid Release version August 01, 2003
  • Latest Rapid Release version September 22, 2016 revision 024
  • Initial Daily Certified version August 01, 2003
  • Latest Daily Certified version September 22, 2016 revision 025
  • Initial Weekly Certified release date August 01, 2003

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

Technical Description

When W32.Mimail.A@mm is run, it does the following:

  1. Copies itself to %Windir%\Videodrv.exe.

  2. Adds the value:


    to the registry key:


    so that W32.Mimail.A@mm runs when you start Windows.

  3. Collects email addresses from all the files except those with the following file extensions:

  4. Writes all the email addresses to the file, %Windir%\eml.tmp, if it can resolve to any IP address.

  5. Captures text from specific windows and sends the data to email addresses that the worm contains.

  6. Sends email messages using its own SMTP engine. For each email address to which the worm wants to send itself, it will:
    • Look up the MX record for the domain name using the DNS server of the current host. If a DNS server is not found, it will default to
    • Acquire the mail server associated with that particular domain.
    • Directly contact the destination server.

      The email has the following characteristics:

      From: admin@<current domain> (The from address may be spoofed to appear that it is coming from the current domain)

      Subject: your account [random string]

      Hello there,
      I would like to inform you about important information regarding your email address. This email address will be expiring. Please read attachment for details.

      Best regards,


  7. contains only one file, Message.htm, which uses a code base exploit to create a copy of the worm named Foo.exe in the Temporary Internet Files folder, and then runs it. The compression method of this file inside the zip file is stored so that compression is not used at all.

    Information about this vulnerability and a Microsoft patch is located at:;en-us;330994. We encourage system administrators to apply the Microsoft patch to prevent infection by this worm.

  8. When the HTML file is executed, it will cause the following registry key to be created:

    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Code Store Database\Distribution Units\{11111111-1111-1111-1111-111111111111}

  9. The worm creates two additional files in the %Windir% folder:
    • Zip.tmp: This is a temporary copy of (30,079 bytes).
    • Exe.tmp: This is a temporary copy of message.html (29,957 bytes).


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.


Removal using the W32.Mimail.A@mm Removal Tool
Symantec Security Response has created a tool to remove W32.Mimail.A@mm, which is the easiest way to remove this threat.

Manual Removal
As an alternative to using the removal tool, you can manually remove this threat.

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.Mimail.A@mm.
  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.Mimail.A@mm, click Delete.

4. Deleting the value from the registry

WARNING: 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:


  5. Exit the Registry Editor.

Writeup By: Atli Gudmundsson