Threat Description



Category: Malware
Type: Virus
Platform: W32
Aliases: SysLock


One unusual "feature" of this virus is that it will search the disk for the string "Microsoft" and change it into "MACROSOFT". The virus will not infect programs if the environment contains SYSLOCK=@.


Automatic action

Once detected, the F-Secure security product will automatically disinfect the suspect file by either deleting it or renaming it.

More scanning & removal options

More information on scanning or removal options is available in the documentation for your F-Secure security product on the Downloads section of our Home - Global site.

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

Contact Support

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

Technical Details


Two minor variants, which will transform the string "Microsoft" into "MACHOSOFT". One is very close to the original SysLock virus, with only one byte different, but the other has been modified somewhat.


Activates in December and plays "Oh, Tannenbaum".


The last variant is 2232 bytes long and known as "Cookie", because it may display the message

I want a COOKIE!  


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