TCP scans are built on the TCP three-way handshake.A three-way handshake is required before a connection is made and data is transferred.The handshake consists of: Sender sending a TCP packet with a synchronized (SYN) bit set Receiver responds with a SYN bit set and an acknowledgment (ACK) bit set Sender responds with an ACK bit set to complete the connectionTCP is a connection-oriented protocol, used to: Establish a connection Restart a failed connection Finish a connectionUses flags to manipulate the TCP protocol with the intent to bypass detection.