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Discovered: July 11, 2003
Updated: February 13, 2007 12:03:44 PM
Also Known As: Proxy-Migmaf [McAfee], Troj/Migmaf-A [Sophos], TROJ_MIGMAF.A [Trend], Win32.Migmaf.A [CA]
Type: Trojan Horse
Systems Affected: Windows

Backdoor.Migmaf is a reverse proxy Trojan Horse that redirects HTTP requests to a master Web server. This enables the creator of the Trojan to hide the real IP address of the Web server, which typically contains pornographic material.

    Backdoor.Migmaf is written in Microsoft Visual C++ and is packed with tElock v0.98.

    There have been reports that Backdoor.Migmaf is distributed with the W32.Sobig.E@mm worm, this has not been confirmed.

    Antivirus Protection Dates

    • Initial Rapid Release version July 14, 2003
    • Latest Rapid Release version November 04, 2019 revision 019
    • Initial Daily Certified version July 14, 2003 revision 002
    • Latest Daily Certified version November 04, 2019 revision 065
    • Initial Weekly Certified release date July 16, 2003

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

    Technical Description

    When Backdoor.Migmaf is executed, it performs the following actions:

    1. Creates a mutex named:


      if this mutex already exists, then Backdoor.Migmaf will terminate.

    2. Checks the first three values of the registry key:

      HKEY_CURRENT_USER\Keyboard Layout\Preload

      to determine whether any of the keyboard input locales are Russian. If any are, then Backdoor.Migmaf will exit.

    3. Adds the value:

      "Login Service"= <location of file>

      to the registry key:


      so that Backdoor.Migmaf is executed each time Windows is restarted.

    4. Attempts to detect a network connection.
      • If the Trojan does not detect a connection, it keeps attempting to do so.
      • If the Trojan detects one, it waits for five minutes, and then continues with its routine.

    5. Tries to determine the connection speed of the current host by reading nine times from, and then by trying to send nine 100 KB URL header packages to Backdoor.Migmaf keeps track of how long it takes to perform these operations, and keeps track of how much data is actually sent and received. This enables it to establish the connection speed.

      Additionally, Backdoor.Migmaf monitors how long this process takes and terminates either step (read or send) if it takes longer than 20 seconds, noting the data accumulated so far.

    6. Establishes a connection to the server (which hosts the Web content) of the Trojan's author.

      This is achieved by first trying to connect to a random IP address (chosen from a set of 81 IP numbers). If the connection is successful, then Backdoor.Migmaf will search for a string of the form '[...]' assuming that whatever is between the brackets will contain a URL to the actual Web server.

      The set of IP addresses is constructed from { 209 | 216 | 78 }.{ 164 | 128 | 12 }.{ 55 | 211 | 216 }.{ 61 | 187 | 210 }

      Backdoor.Migmaf will try this until it gets a response that contains the letters '[' and ']'.

    7. After establishing a connection to the Web server of the Trojan's creator, Backdoor.Migmaf will then submit information about the current host to it, including:
      • The platform (Windows NT/2000/XP or 95/98/Me)
      • Send transfer speed
      • Receive transfer speed
      • A timestamp reprecentation modulo 10000, in minutes, for when the backdoor was started
      • A timestamp reprecentation modulo 10000, in minutes, for the current time on the host

        A sample URL submission string will look like this:

        http:/ /

        which would indicate a 9x platform with 56 K transfer capabilities.

        The full format of this string is:

        http:/ /IP/[version][rand1][start time][platform is 9x][send rate][receive rate][timer now]

        This is formatted with the C string:

        http:/ /%d.%d.%d.%d/?h=yes&i=%02d%09d%04d%01d%07d%07d%04d

    8. After submitting the host information, Backdoor.Migmaf establishes a connection on the host computer, as the Trojan's creator directs, which he or she can now use either to redirect his/her own traffic through, or for others to connect through, without requiring the Trojan's creator to show his/her actual IP address (the actual Web server's address).
    • Backdoor.Migmaf contains the text "disclaimer: used for bandwidth speed testing only."
    • Backdoor.Migmaf only runs under the operating systems, NT4.0 SP4 and later and Windows 98 and later, which have Internet Explorer 3.0 or later installed.


    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.


    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 Backdoor.Migmaf.
    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 Backdoor.Migmaf, click Delete.

    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:

      Login Service

    5. Exit the Registry Editor.

    Writeup By: Scott Gettis