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Discovered: December 07, 2004
Updated: February 13, 2007 12:30:51 PM
Also Known As: Maslan.A [F-Secure], Net-Worm.Win32.Maslan.a [Kaspe, W32/Maslan-A [Sophos], WORM_MASLAN.A [Trend Micro]
Type: Worm
Systems Affected: Windows

W32.Maslan.A@mm is a mass-mailing worm that opens a back door and exploits system vulnerabilities on the compromised computer. The worm also steals passwords and uses rootkit techniques.

Antivirus Protection Dates

  • Initial Rapid Release version December 07, 2004
  • Latest Rapid Release version August 08, 2016 revision 023
  • Initial Daily Certified version December 07, 2004
  • Latest Daily Certified version August 09, 2016 revision 001
  • Initial Weekly Certified release date December 08, 2004

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

Technical Description

When W32.Maslan.A@mm runs, it does the following:

  1. Creates some of the following files:
    • %System%\___j.dll (the part of the worm that is injected into svchost.exe)
    • %System%\___r.exe (the main worm executable)
    • %System%\___synmgr.exe (detected as W32.IRCBot)
    • %System%\___n.exe (detected as W32.IRCBot)
    • %System%\___e (contains a MIME encoder version of the worm)
    • %System%\___u (contains a dropper for the worm)

      Note: %System% is a variable that refers to the System folder. By default this is C:\Windows\System (Windows 95/98/Me), C:\Winnt\System32 (Windows NT/2000), or C:\Windows\System32 (Windows XP).

  2. Injects ___j.dll into the svchost.exe process.

  3. Deletes and recreates the files:
    • %System%\Alaftp
    • %System%\AlaMail
    • %System%\AlaScan
    • %System%\AlaDdos
    • %System%\___prior
    • %System%\___m
    • %System%\___t

      The worm uses these to store data gathered from the infected computer.

  4. Adds the values:

    "Microsoft Synchronization Manager" = "___synmgr.exe"
    "Microsoft Windows DHCP" = "___r.exe"

    to the registry key:


    so that the worm runs every time Windows starts.

  5. Adds the value:

    "Microsoft Synchronization Manager" = "___synmgr.exe"

    to the registry key:


    so that the worm runs every time Windows starts.

  6. Starts ___r.exe.

    Note: The original file that was executed writes to its own memory space, causing it to crash. The other processes that the worm started continue running.

  7. Terminates the following processes:
    • _AVPM.EXE
    • _AVPCC.EXE
    • _AVP32.EXE
    • ZAPSETUP3001.EXE
    • ZONALM2601.EXE
    • RESCUE32.EXE
    • NC2000.EXE
    • NAVW32.EXE
    • NAV.EXE
    • DRWEB32.EXE
    • AVPTC32.EXE
    • AVPM.EXE
    • AVPDOS32.EXE
    • AVP32.EXE
    • AVP.EXE
    • AVKWCTl9.EXE

  8. Uses rootkit techniques to prevent the files and processes whose names start with ___ (three underscore characters) from being visible to users. This may also cause the Task Manager to fail to start.

  9. Scans for computers and tries to exploit the DCOM RPC Vulnerability (described in Microsoft Security Bulletin MS03-026) using TCP port 135.

  10. Opens a back door by connecting to a remote IRC server to receive instructions from a remote attacker.

  11. Monitors Internet Explorer windows that contain one of the following strings:
    • evocash
    • e-bullion
    • e-gold
    • mail
    • bank
    • trade
    • paypal

      When the worm detects a window containing one of the above strings, it logs keystrokes and sends this information to a remote web site.

  12. Searches the hard drive for the files that contain the following substrings in their paths:
    • distr
    • download
    • setup
    • share

      and have one of the following extensions:
    • rar
    • zip
    • pif
    • exe

      The worm searches for files that meet the above criteria and are greater in size than %System%\___u. The worm then creates a back up copy of the file in the subfolder \___b, with the same file name and a similar file path.

      The worm then overwrites the original file with a copy of %System%\___u. This file will have the same file name, file path, file size, and icon as the original file, but with a .exe extension.


      If the worm finds the following file:


      it overwrites the above file with the following file:

      C:\test\share\example.exe (a copy of %System%\___u)

      and creates the file:

      C:\___b\test\share\example.zip (a back up of the original file)

  13. Collects email addresses from the files with the following extensions:
    • xml
    • xls
    • wsh
    • wab
    • uin
    • txt
    • tbb
    • stm
    • shtm
    • sht
    • php
    • oft
    • ods
    • nch
    • msg
    • mm
    • f
    • mht
    • mdx
    • mbx
    • jsp
    • htm
    • eml
    • dhtm
    • dbx
    • cgi
    • cfg
    • asp
    • adb

      Avoids email addresses that contain the following substrings:
    • mail.com
    • freemail.com
    • hotmail.com
    • yahoo.com
    • msn.com
    • aol.com
    • subscribe
    • accoun
    • certific
    • listserv
    • ntivi
    • admin
    • mozilla
    • utgers.ed
    • tanford.e
    • pgp
    • acketst
    • secur
    • isc.o
    • isi.e
    • ripe.
    • arin.
    • sendmail
    • rfc-ed
    • ietf
    • iana
    • usenet
    • fido
    • linux
    • kernel
    • google
    • ibm.com
    • fsf.
    • gnu
    • mit.e
    • bsd
    • math
    • unix
    • berkeley
    • foo.
    • mysqlruslis
    • nodomai
    • mydomai
    • example
    • inpris
    • borlan
    • sopho
    • panda
    • syma
    • avp
    • abuse
    • www
    • spam
    • spm
    • test
    • page
    • the.bat
    • gold-certs
    • feste
    • submit
    • not
    • help
    • service
    • privacy
    • somebody
    • soft
    • contact
    • site
    • rating
    • bugs
    • you
    • your
    • someone
    • anyone
    • nothing
    • nobody
    • noone
    • webmaster
    • postmaster
    • samples
    • info
    • root

  14. Sends itself to email addresses gathered from the infected computer. The email has the following characteristics:

    From: (Spoofed)

    Subject: 123

    Attachment: PlayGirls2.exe

    Message Body:

    Hello [Random name]
    Best regards,
    [Random name]


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. Restart the computer in Safe mode or VGA mode.
  4. Run a full system scan and delete all the files detected as W32.Maslan.A@mm.
  5. Restore files.
  6. Delete files created by the threat.
  7. Reverse the changes made to the registry.
For 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:
When you are completely finished with the removal procedure and are satisfied that the threat has been removed, re-enable System Restore by following the instructions in the aforementioned documents.

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. 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 daily. 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.Maslan.A@mm, click Delete.

5. To restore files
  1. Navigate to the ___b folder in the root directory of your infected Hard Disk (e.g. C:\___b )
  2. Select all files and folders in the ___b folder.
  3. On the Taskbar click Edit > Copy
  4. Go back to your root directory and click Edit > Paste
  5. Delete the ___b folder.

6. To delete files created by the threat
Navigate to and delete the following files:
  • %System%\___e
  • %System%\___m
  • %System%\___t

7. To reverse the changes made to 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. Type regedit

    Then click OK.

  3. Navigate to the key:


  4. In the right pane, delete the values:

    "Microsoft Synchronization Manager" = "___synmgr.exe"
    "Microsoft Windows DHCP" = "___r.exe"

  5. Navigate to the key:


  6. In the right pane, delete the values:

    "Microsoft Synchronization Manager" = "___synmgr.exe"

  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: Paul Mangan