1. A method of performing an anti-virus scan of a file system, the method comprising: for a file stored in the file system, obtaining intermediate scanning results prior to a scan of the file being completed; storing the intermediate scanning results in a database; during a subsequent anti-virus scan of the file system, prior to performing an intermediate scan of the file stored in the file system, determining if intermediate scanning results relating to the file are available in the database; and where intermediate scanning results are available in the database for a particular type of intermediate scan, not performing that intermediate scan of the file, and where intermediate scanning results are not available in the database for a particular type of intermediate scan, performing that intermediate scan of the file.