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.
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 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.