There is no virus by this name. However, we sometimes get queries about this, since Microsoft Office's 'Fast Find' feature creates hidden files named like this to root directory: __OFIDX.FFA, __OFIDX.FFL, __OFIDX0.FFX. This is harmless.
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.