What is SYN Attack

A SYN attack exploits a basic weakness found in the TCP/IP protocol. A standard TCP session consists of the two communicating hosts exchanging a SYN | SYN/ACK | ACK. The expected behavior is that the initiating host sends a SYN packet, to which the responding host will issue a SYN/ACK and wait for an ACK reply from the initiator. With a SYN attack, or SYN flood, the attacker simply sends only the SYN packet, leaving the victim waiting for a reply.

The attack occurs when the attacker sends thousands and thousands of SYN packets to the victim, forcing them to wait for replies that never come. While the host is waiting for so many replies, it can’t accept any legitimate requests, so it becomes unavailable, thus achieving the purpose of a DoS attack.




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