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Discovered: September 06, 2004
Updated: February 13, 2007 12:27:10 PM
Type: Worm
Systems Affected: Windows

W32.Blackmal.C@mm is a mass-mailing worm that lowers security settings by deleting files associated with security applications. It sends a copy of itself to all email addresses gathered from the MSN Messenger and Yahoo Pager address books as well as from files with either .htm or .dbx extensions.

Antivirus Protection Dates

  • Initial Rapid Release version September 06, 2004
  • Latest Rapid Release version May 07, 2019 revision 006
  • Initial Daily Certified version September 06, 2004
  • Latest Daily Certified version May 07, 2019 revision 008
  • Initial Weekly Certified release date September 08, 2004

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

Technical Description

When W32.Blackmal.C@mm is executed, it performs the following actions:

  1. Opens Windows Media Player.

  2. Creates the following copies of itself:
    • %System%\Connection.exe
    • %System%\Task.exe
    • %System%\hhm.exe
    • \winnt\volume\winhelp.exe
    • \winnt\volume\twunk_32.exe
    • %System%\sound_223.mp3_________________________________________________________.scr
    • %System%\movie_05.MP3_________________________________________________________.exe
    • %System%\PaltlkRoom.wav_________________________________________________________.scr
    • %System%\%System%\Video_live.mpg_________________________________________________________.exe

  3. Drops the following files:
    • %System%\About_Blackworm.C.txt
    • %System%\ossmtp.dll

      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).
  4. Adds one of the following values:

    "(default)" = "C:\winnt\volume\[twunk_32.exe]"
    "(default)" = "C:\winnt\volume\[winhelp.exe]"

    to the registry key:


    so that the worm is executed every time Windows starts.

  5. Adds the value:


    to the registry key:

    HKEY_CURRENT_USER\Software\Nico Mak Computing\WinZip\caution

  6. Adds the values:

    Name = "BlackWorm"
    SN = "2AD00ED6"

    to the registry key:

    HKEY_CURRENT_USER\Software\Nico Mak Computing\WinZip\WinIni

  7. Deletes the following registry values:
    • _Hazafibb
    • au.exe
    • ccApp
    • defwatch
    • Explorer
    • erthgdr
    • gigabit.exe
    • JavaVM
    • KasperskyAv
    • key
    • MCUpdateExe
    • MCAgentExe
    • McRegWiz
    • McVsRte
    • McAfeeVirusScanService
    • msgsvr32
    • NAV Agent
    • Norton Antivirus AV
    • OLE
    • PCClient.exe
    • PCCIOMON.exe
    • pccguide.exe
    • PccPfw
    • PCCClient.exe
    • rtvscn95
    • reg_key
    • ScriptBlocking
    • system.
    • Sentry
    • ssate.exe
    • Services
    • tmproxy
    • Taskmon
    • Traybar
    • Task
    • VirusScan Online
    • VSOCheckTask
    • vptray
    • Windows Services Host
    • winupd.exe
    • Windows Update
    • win_upd.exe
    • winupdt
    • wersds.exe

      from the following registry keys:
    • HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
    • HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunServices

  8. Deletes the following files:
    • C:\Program Files\Norton AntiVirus\*.exe
    • C:\Program Files\McAfee\McAfee VirusScan\Vso\*.*
    • C:\Program Files\McAfee\McAfee VirusScan\Vso
    • C:\Program Files\McAfee\McAfee VirusScan\Vs
    • C:\Program Files\Trend Micro\PC-cillin 2002\*.exe
    • C:\Program Files\Trend Micro\PC-cillin 2003\*.exe
    • C:\Program Files\Trend Micro\Internet Security\*.exe
    • C:\Program Files\NavNT\*.exe
    • C:\Program Files\HyperTechnologies\Deep Freeze\*.exe

  9. May copy itself to open network shares as "Good Music.scr".

Email routine details
The worm uses its own SMTP engine to email itself to all the email addresses listed in MSN Messenger, Yahoo Pager, as well as in all the files whose extensions are either .htm or .dbx.

It also attempts to send the email through the default SMTP server address, which the infected computer uses. If the worm cannot find this information, then it will use one of the many SMTP server addresses that are hard-coded into the worm.

Attachments: The worm selects one of the files dropped in the %System% folder as an attachment with one of the following extensions:
  • .zip
  • .z
  • .gz
  • .tgz
In addition, it may also attach a .jpg file, which is a pornographic image.

From : One of the following email addresses:
  • ack_back06@mail.com
  • thomas_gay6@iopus.com
  • sandra@oxygen.com
  • linda200@gmail.com
  • user377@worldsex.com
  • gustes@msn.com
  • admin@newmovies.com
  • hot_woman2362@freevideos.net
  • lost_love705@yahoo.com
  • King_sexy@hotmal.com

Subject: One of the following:
  • For all
  • Hello
  • Please reactive now.
  • Thanks
  • Update
  • Please reactive now
  • Thank you
  • please reactive

Message: One of the following.
  • see the attached <link to a gif image> <link to a gif image>
  • how are you? see the file <link to a gif image> <link to a gif image>
  • video <link to a gif image> <link to a gif image> <link to a gif image>
  • see the movie <link to a gif image> <link to a gif image>
  • enjoy <link to a gif image>

Note: The email messages that the worm creates may contain a .gif file. This file is clean and safe to be opened.


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. Restart the computer in Safe Mode or VGA mode.
  3. Reverse the changes that the worm made to the registry.
  4. Reinstall your Symantec antivirus program.
  5. Update the virus definitions.
  6. Restart the computer in Safe Mode or VGA mode.
  7. Run a full system scan and delete all the files detected as W32.Blackmal.C@mm

    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:

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 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.

3. To reverse the changes made to 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 following keys:


  4. In the right pane, delete either of the following values:

    "(default)" = "C:\winnt\volume\[twunk_32.exe]"
    "(default)" = "C:\winnt\volume\[winhelp.exe]"
  5. Navigate to the following keys:

    KEY_CURRENT_USER\Software\Nico Mak Computing\WinZip\caution
  6. In the right pane, delete the value:

  7. Navigate to the following keys:

    KEY_CURRENT_USER\Software\Nico Mak Computing\WinZip\WinIni
  8. In the right pane, delete the values:

    Name = "BlackWorm"
    SN = "2AD00ED6"

  9. Exit the Registry Editor

4. To reinstall your Symantec antivirus program
As this virus attempts to remove the files and registry keys that your Symantec antivirus program uses, you may need to re-install the program. If your Symantec antivirus program is not working properly, uninstall, and then reinstall it.

5. 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 instruction

6. 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.

7. 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.Blackmal.C@mm, click Delete.

Writeup By: Fergal Ladley