Abstract: A method for providing security to a computer network by selectively blocking network transmissions from selected IP addresses comprising the steps of: establishing a risk threshold whereby transmissions from IP addresses exceeding said risk threshold are selectively blocked; receiving a network transmission having an originating IP address and payload; analyzing the payload of said transmission and assigning a current risk rating to said IP address on the basis of said analysis; comparing the originating IP address of said transmission to a database of known IP addresses, each of said said previous cumulative assigned risk rating being based on at least one previous transmission from a known IP address; known IP addresses having a previous cumulative assigned risk rating, assigning a new cumulative risk rating to said originating IP address, said new cumulative risk rating being the sum of said current risk rating and said previous cumulative assigned risk rating for said originating IP address, with the pro