Patent ID: 7310817

Claim:
A computer program product embodied on a tangible computer readable medium for controlling a computer to detect malware, said computer program product comprising: file access request receiving logic operable to receive at an assessment computer a file access clearance request from a requesting computer, said file access clearance request including data identifying a computer file to be accessed by said requesting computer; file access clearance response generating logic operable in dependence upon said data identifying said computer file to determine if said computer file has previously been assessed as not containing malware and to generate file access clearance response; and file access clearance response transmitting logic operable to transmit said file access clearance response to said requesting computer; wherein said assessment computer stores a database of computer files and said database includes for each computer file a persistence flag indicating whether an entry relating to said computer file should be purged from said database during purge operations; wherein said database includes for each computer file fields specifying a filename of said computer file, data identifying said requesting computer and a storage location of said computer file, and a checksum value calculated from said computer file; wherein said assessment computer is operable in at least a higher level security mode and a lower level security mode, said assessment computer serving to deny access to a greater range of computer files when operating in said higher level security mode compared with said lower level security mode.