Patent ID: 6094731
Filing Date: 2000-07-25
Classification: G06F,H04L

Abstract:
A computer-based method for examining a file that is transmitted over a computer network from an originating computer to a recipient computer to determine whether a computer virus is present within said file, said file containing at least one sector, the method comprising the steps of:causing the originating computer to:scan the file by an associated antivirus module while storing into a first storage area an identification of each file sector that is scanned and a hash value of each sector that is scanned; andcalculate a digital signature of a computed message digest of contents of the first storage area; andcausing the recipient computer to:compute a hash value for each file sector that was scanned by the originating computer, to generate a computed hash value;compare each computed hash value with the hash value stored within said first storage area for the corresponding sector, wherein, when any computed hash value fails to match a corresponding stored hash value for any sector, the entire file is rescanned;examine the authenticity of the digital signature by comparing a decrypted message digest with the computed message digest; andrescan the entire file when the decrypted message digest does not match the computed message digest.