Question

What type of scan sends a SYN flag, receives an SYN/ACK, then sends a RST?

Option 1: XMAS
Option 2: FIN
Option 3: Half-open
Option 4: None of the above

Answer 1

A Half-open scan sends a SYN flag, receives an SYN/ACK and then sends a RST. It's a method used to probe for open ports without establishing a full TCP connection.

Step-by-step explanation:

The type of scan that sends a SYN flag, receives an SYN/ACK, and then sends a RST is called a Half-open scan. This scanning method is also known as a SYN scan or a stealth scan. The process works as follows:

1. A scanning computer sends a SYN packet as if it is initiating a normal TCP connection.
2. The target machine responds with a SYN/ACK packet if the port is open.
3. Rather than completing the three-way handshake with an ACK, the scanning computer responds with a RST (reset), closing the connection before it is fully established.

This technique is used to probe for open ports without establishing a full TCP connection, which can be logged or detected by some intrusion detection systems.