Threat description




VBS/Mcon is a worm that spreads via open network shares and mIRC.


Automatic action

Depending on the settings of your F-Secure security product, it will either automatically delete, quarantine or rename the suspect file, or ask you for a desired action.

More scanning & removal options

More information on the scanning and removal options available in your F-Secure product can be found in the Help Center.

You may also refer to the Knowledge Base on the F-Secure Community site for more information.

Contact Support

F-Secure customers can request support online via the Request support or the Chat forms on our Home - Global site.

Technical Details


When the worm is executed, it first checks if the "Fonts" subdirectory in the Windows installation directory contains the worm. If the file is not found, the worm copies itself there using a filename "ttfloader.vbs". Then the worm executes the copy from the "Fonts" directory and deletes the original file.

If the original file was not named "ttfloader.vbs" or was not executed from the Windows' Startup directory the worm shows a message box with the following text:


Next the worm will add itself to the registry, so it will be executed each time when the system is restarted.

Depending an a random number, the worm may change the Internet Explorer page to

The worm goes trough all drives in the system and if the drive is a local fixed disk, it copies itself to the root of the drive and to the following directories:

    pub     ftproot     wwwroot   

or if the name of the directory contains any of the following strings:

    my     download     upload     share     game     warez   

The worm copies itself using a random file name taken from user's Recent directory, with a number of spaces and a ".vbs" extension appended to it. An attempt is made to hide the file by changing the file attributes as well.

It also removes following directories, if found:

    chode     foreskin     dickhair 

If the drive is a network or removable drive, then VBS/Mcon.A copies itself to the root of the drive, and any directory that contains one of the following strings:

   my     share     download     downloads 

Also, if Windows' Startup directory is found, the worm copies itself there as "ttfloader.vbs".

The worm deletes following files regardless of the drive

   mscfg.exe     ashield.pif     netstat.pif     network.vbs     mscfg.vbs     winsock.vbs     a24.vbs 

If VBS/Mcon.A founds a mIRC installation directory, the worm copies itself to the Windows' Fonts directory using name "sndload.vbs" and replaces the "script.ini" file with its own.

Next the worm chooses a random IP addess within some limits and uses the ping utility to check if a machine responds at that address. If the machine exist, it attempts to connect to each share on the remove machine.

If the connection is established, the worm will go through all directories in the shared drive copying itself there in the same way it does with removable and network drives above.


VBS/Mcon.B is modified variant of VBS/Mcon.A. The filename, that the worm uses in Windows' Fonts directory is changed to "ttfloads.vbs".

Additionally this variant copies itself to the Windows' System directory as "ttfload.dll".

Submit a Sample

Suspect a file or URL was wrongly detected?
Send it to our Labs for further analysis

Submit a Sample

Give And Get Advice

Give advice. Get advice. Share the knowledge on our free discussion forum.

More Info