1. A computer program product comprising a computer program operable to control a computer to detect a known computer program within a packed computer file, said packed computer file being unpacked upon execution, said computer program comprising: resource data reading logic operable to read resource data within said packed computer file, said resource data specifying program resource items used by said known computer program and being readable by a computer operating system without dependence upon which unpacking algorithm is used by said packed computer file; and resource data comparing logic operable to compare said resource data with characteristics of resource data of said known computer program to detect a match with said known computer program indicative of said packed computer file containing said known computer program.