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.
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.