What is the difference between TCP Scans and SYN Scans?

1 Answer 1


TCP scanning refers on scanning a target network for TCP connections , how you are going to look for the connection defines different techniques. Both Connect Scan and SYN Scan are types of TCP Scans to determine if the probed server has active TCP connections

SYN Scan is a type of TCP scanning where you probe the target network sending SYN packets, at all desired ports , to initiate a three-way handshake . The server will respond with SYN-ACK for every open port and a RST response for closed ones.After that you don't reply to the server to complete the 3-way-handshake and open a connection.

Connect Scan is another type of TCP Scan similar to SYN Scan but this time after receiving a SYN-ACK response from the server you reply with ACK response completing the 3-way-handshake and establishing a connection to the server, which will take more resources and time to complete.

  • So they change in a way of scanning. In addition TCP scan (connect scan) uses the OS system call, connect, to check the port status. SYN Scan uses, a packet with SYN bit set to 1, called SYN PACKET, to check the port status. Feb 9, 2019 at 10:23
  • just edited my answer
    – Bokis
    Feb 9, 2019 at 11:59
  • Note that, depending on the platform, you may need elevated privileges (root) to perform a SYN scan. Also the scans have different profiles that can create different artifacts on the targets. Feb 10, 2019 at 1:41

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