VBS/Mcon is a worm that spreads via open network shares and mIRC.
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.
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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:
FILE I/O ERROR
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 www.zonelabs.com.
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".
Technical Details: Katrin Tocheva and Sami Rautiainen, F-Secure; January 2001