A procedure and implementations thereof are disclosed that significantly reduce the amount of time necessary to perform a virus scan. A file signature is created each time a file is modified (i.e., with each "file write" to that file). The file signature is inserted, with a date stamp, into the file attributes. The virus scan program checks the previously-created file signature against the virus signature file instead of creating the file signature for every file during the virus scan. Checks to ensure that the file signature is secure, and is valid and up to date, are also implemented. Only if the file signature is not valid and up-to-date does the virus scan program create a new file signature at the time of the running of the virus scan.