This virus first adds 1-16 bytes to the files it infects, so they end on a paragraph boundary. Then 669 additional bytes, containing the virus itself are written to the end.
On any Saturday the 14th, the first 100 logical sectors of drive C, then B, then A are overwritten with rubbish.
Once detected, the F-Secure security product will automatically disinfect the suspect file by either deleting it or renaming it.
More information on 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.