Patent ID: 7979694

Claim:
A method for authenticating an Internet Protocol (IP) source address in a Transmission Control Protocol (TCP) communication directed over a network to a target computer, the method comprising: intercepting a SYN request packet from the IP source address to open a connection to the target computer in accordance with a TCP three-way handshake procedure; sending to the IP source address a reply to the intercepted SYN request packet that deviates from the three-way TCP handshake procedure by sending a TCP ACK packet as a reply to the intercepted SYN request packet instead of a SYN ACK packet when opening a new TCP connection; analyzing a response from the IP source address to the TCP ACK reply in order to make an assessment of legitimacy of the IP source address; and upon determining, based on the assessment, that the IP source address is legitimate, permitting the target computer to complete the handshake procedure so as to open the connection with the IP source address.