PING Scan (-sP) TCP SYN Scan (-sS) TCP Connect() Scan (-sT) UDP Scan (-sU)

Source System sends a SYN request to the Target but a Port number is added to the request in this case. The Target System will respond with a SYN/ ACK (Sync/Acknowledgement) to the Source if the specified Port is open. The Source System responds with a RST (Reset) to the Target to close the connection. The Target System can respond with a RST/ACK (Reset/Acknowledgement) to the Source System.

Source System sends a SYN request to the Target and a Port number is added to the request. The Target responds with a RST (Reset) since the Port is closed.

Source System sends a SYN request to the Target and the Port number is added to the request. No response is received since it was Filtered by the Firewall.

Source System sends a SYN request to the Target but a Port number is added to the request in this case. The Target System will respond with a SYN/ ACK (Sync/Acknowledgement) to the Source if the specified Port is open. The Source System responds with an ACK (Acknowledgement) to the Target to finish the session creation. The Source System then sends the Target System a RST (Reset) packet to close the session. The Target System can respond with a RST/ACK (Reset/Acknowledgement) to the Source System.