A TCP SYN flood is a type of distributed denial-of-service (DDoS) attack that aims to overwhelm the target system with a flood of connection requests. The attack is named after the SYN packet, which is used to initiate a TCP (Transmission Control Protocol) connection. When the target system receives a SYN packet, it typically responds with a SYN-ACK packet to acknowledge receipt and establish a connection. However, in a SYN flood attack, the attacker sends a large number of SYN packets to the target system, often from multiple sources, without intending to complete the connection. This can consume the target system’s resources, such as memory and network buffers, and eventually cause it to become unavailable or unstable. Modern operating systems have been optimized to reduce the amount of memory consumed by incomplete TCP connections.