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.
Detailed instructions for F-Secure security products are available in the documentation found in the Downloads section of our Home - Global site.
You may also refer to the Knowledge Base on the F-Secure Community site for further assistance.