This virus activates on Monday the 23rd of any month not in 1990, formatting the beginning of the hard disk. It may also delete files, as they are opened. The increase in length of infected files is not visible when a DIR command is given.
This virus belongs to the Jerusalem family.
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.