Discovered: July 19, 2004
Updated: February 13, 2007 12:25:29 PM
Also Known As: W32/Mydoom.n@MM [McAfee], WORM_MYDOOM.L [Trend], W32/MyDoom-N [Sophos], I-Worm.Mydoom.l [Kaspersky], Win32.Mydoom.N [Computer Assoc
Type: Worm
Systems Affected: Windows


The W32.Mydoom.L@mm mass-mailing worm:

  • Uses its own SMTP engine to send itself to all the email addresses that it finds from an infected system.
    The email has an attachment with a .bat, .cmd, .com, .exe, .pif, .scr, or .zip extension.
  • The attachment name may contain a randomly selected domain, which was found on the sender's system. For example, the attachment name could contain fakedomain.com if the address x@fakedomain.com was harvested.
  • Contains keylogging capabilities. The From field of the email is spoofed.
  • Acts as a backdoor on infected systems.
  • Is written in C++ and is packed with UPX.

Note: Virus definitions 60719am (extended version July 19, 2004, rev. 39) and earlier, released on July 19, 2004, detect this threat as W32.Beagle.AF@mm.


Antivirus Protection Dates

  • Initial Rapid Release version July 19, 2004
  • Latest Rapid Release version June 14, 2018 revision 004
  • Initial Daily Certified version July 19, 2004
  • Latest Daily Certified version June 14, 2018 revision 007
  • Initial Weekly Certified release date July 19, 2004

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

Writeup By: Yana Liu

Discovered: July 19, 2004
Updated: February 13, 2007 12:25:29 PM
Also Known As: W32/Mydoom.n@MM [McAfee], WORM_MYDOOM.L [Trend], W32/MyDoom-N [Sophos], I-Worm.Mydoom.l [Kaspersky], Win32.Mydoom.N [Computer Assoc
Type: Worm
Systems Affected: Windows


When W32.Mydoom.L@mm is run, it does the following:

  1. Copies itself as %Windir%\lsass.exe.

    Note: %Windir% is a variable. The XXthreattypeXX locates the Windows installation folder (by default, this is C:\Windows or C:\Winnt) and copies itself to that location.

  2. Use a randomly named .txt file in %Temp% for logging purposes.

    Note: %Temp% is a variable. The worm locates the temporary folder and copies itself to that location. By default, this is C:\Windows\TEMP (Windows 95/98/Me/XP) or C:\WINNT\Temp (Windows NT/2000).

  3. Adds the value:

    "Traybar" = "%Windows%\lsass.exe"

    to the registry key:

    HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run

    so that the worm runs when you start Windows.

  4. Creates the following registry key:

    HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\POSIX
    HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\POSIX

  5. Attempts to copy itself to all the folders whose names contain the following strings:
    • incoming
    • ftproot
    • download
    • shar

      The files dropped to these folders will have the following names:
    • index
    • Kazaa Lite
    • Harry Potter
    • ICQ 4 Lite
    • WinRAR.v.3.2.and.key
    • Winamp 5.0 (en) Crack
    • Winamp 5.0 (en)

      with one of the following extensions:
    • exe
    • com
    • ShareReactor.com
    • scr

  6. Opens a backdoor on TCP port 1042.

  7. Gathers email addresses from the files with the following extensions on a compromised system:
    • doc
    • txt
    • htm
    • html

  8. Uses its own SMTP engine to send itself to the email addresses that it finds. The email message that the worm constructed typically has the following properties:

    From: Spoofed, using one of the email addresses gathered from the system, or the worm may generate an email address using the following strings:
    • Postmaster
    • Mail Administrator
    • Automatic Email Delivery Software
    • Post Office
    • The Post Office
    • Bounced mail
    • Returned mail
    • MAILER-DAEMON
    • Mail Delivery Subsystem

    Subject:
    May be one of the following:
    • say helo to my litl friend
    • click me baby, one more time
    • hello
    • hi
    • error
    • status
    • test
    • report
    • delivery failed
    • Message could not be delivered
    • Mail System Error - Returned Mail
    • Delivery reports about your e-mail
    • Returned mail: see transcript for details
    • Returned mail: Data format error

    Message: The message body is one of the following:
    • The original message was included as attachment

    • Message could not be delivered

    • This Message was undeliverable due to the following reason:

      Your message was not delivered because the destination computer was
      not reachable within the allowed queue period. The amount of time
      a message is queued before it is returned depends on local configura-
      tion parameters.

      Most likely there is a network problem that prevented delivery, but
      it is also possible that the computer is turned off, or does not
      have a mail system running right now.

      Your message was not delivered within [random number] days:
      Host [hostname of spoofed from address] is not responding.

      The following recipients did not receive this message:
      [spoofed from address]

      Please reply to postmaster [hostname of spoofed from address]
      if you feel this message to be in error.

    • The original message was received at [time]
      from [To address of message]

      ----- The following addresses had permanent fatal errors -----
      [to address of message]
      ----- Transcript of session follows -----
      while talking to [hostname of To address].:
      >>> MAIL From:[From address of message]
      <<< 501 [hostname of From address]... Refused

    • The original message was received at [time]
      from [From address of message]

      ----- The following addresses had permanent fatal errors -----
    Attachment: The worm may generate an attachment file name from the domain name of the email addresses that are gathered on the system. The attachment name may also be one of the following:
    • <blank>
    • attachment
    • document
    • file
    • letter
    • mail
    • message
    • readme
    • text
    • transcript
    with one of the following as an extension:
    • bat
    • cmd
    • com
    • exe
    • pif
    • scr
    • zip
    The worm will not send itself to the addresses containing the following strings:
    • .gov
    • .mil
    • abus
    • accoun
    • admi
    • anyone
    • arin.
    • avp
    • bar.
    • bug
    • contact
    • crosoft
    • domain
    • example
    • feste
    • foo.
    • gmail
    • gnu.
    • gold-certs
    • google
    • gov.
    • help
    • hotmail
    • info
    • james
    • john
    • labs
    • listserv
    • master
    • math
    • microsoft
    • msn.
    • nobody
    • noone
    • not
    • nothing
    • ntivi
    • ophos
    • page
    • panda
    • privacycertific
    • rarsoft
    • rating
    • ripe.
    • root
    • sales
    • sample
    • sarc.
    • seclist
    • secur
    • service
    • sf.net
    • site
    • soft
    • someone
    • sourceforge
    • spam
    • spersk
    • submit
    • suppor
    • syma
    • the.bat
    • update
    • uslis
    • winzip
    • you
    • your


Recommendations

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: Yana Liu

Discovered: July 19, 2004
Updated: February 13, 2007 12:25:29 PM
Also Known As: W32/Mydoom.n@MM [McAfee], WORM_MYDOOM.L [Trend], W32/MyDoom-N [Sophos], I-Worm.Mydoom.l [Kaspersky], Win32.Mydoom.N [Computer Assoc
Type: Worm
Systems Affected: Windows


Removal using the Removal Tool
Symantec Security Response has developed a removal tool to clean the infections of W32.Mydoom.L@mm. This is the preferred method in most cases.


Manual Removal
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. Restart the computer in Safe mode or VGA mode.
  4. Run a full system scan and delete all the files detected as W32.Mydoom.L@mm.
  5. Delete the values that were added to the registry.

For specific details on each of these steps, read the following instructions.
  1. To disable 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:
  2. To update 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. To restart the computer in Safe mode or VGA mode
    Shut down the computer and turn off the power. Wait for at least 30 seconds, and then restart the computer in Safe mode or VGA mode.
    • For Windows 95, 98, Me, 2000, or XP users, restart the computer in Safe mode. For instructions, read the document, "How to start the computer in Safe Mode."
    • For Windows NT 4 users, restart the computer in VGA mode.

  4. To scan for and delete 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.Mydoom.L@mm, click Delete.

  5. To delete the values from the registry

    Important:
    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 > Run.

    2. In the Open box, type: regedit

      Then click OK.

    3. Navigate to the key:

      HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run

    4. In the right pane, delete the value:

      "Traybar" = "%Windows%\lsass.exe"

    5. Navigate to the key and delete it:

      HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\POSIX

    6. Navigate to the key and delete it:

      HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\POSIX

    7. Exit the Registry Editor.

    8. Restart the computer in Normal mode. For instructions, read the section on returning to Normal mode in the document, "How to start the computer in Safe Mode."


Writeup By: Yana Liu