TCP spoofing

TCP performance degrades when used over connections with high Bandwidth Delay Product evident mostly in satellite networks. TCP performance degrades also in networks with high rate of packet loss. Due to its innate nature, TCP is not able to reach optimum window size in these environments. TCP uses algorithms such as three way handshake for startup, sequence numbers and acknowledgments for error free data transfer and slow start for congestion control which significantly delays connection. All these adversely affect the effective bandwidth of TCP connection.

To improve the experience of the user end, protocol spoofing is done. An intermediate device (such as a modem or a router) between the user and the remote end which the user is trying to connect to, simulates ("spoofs") the remote end. The intermediate device then uses a more appropriate protocol to communicate with a compatible remote device that performs the equivalent spoof at the other end of the communications link. This mechanism is also known as TCP Splitting as the network is now split into TCP and the protocol that is most suitable for the intermediate connection.

Spoofing is also used by hackers to break into other networks by simulating a trusted computer of the network.