CompTIA PenTest+ Practice Test

Which scanning technique sends TCP packets to determine if ports are open or closed?

1. FIN scan

2. TCP connect scan

3. ACK scan

4. Null scan

The correct answer is: ACK scan

The technique that sends TCP packets to determine if ports are open or closed operates by utilizing a method that requests a connection with the port. In a TCP connect scan, the scanning tool attempts to establish a full TCP connection with the target machine at the specified port. If the port is open, a successful three-way handshake occurs, confirming that the port is indeed open. If the port is closed, the target system will respond with a TCP RST (reset) packet, indicating that the connection attempt was rejected. This method is straightforward and reliable for identifying open and closed ports, making it a frequently used scanning technique in network security assessments. The other scanning techniques mentioned serve different purposes: a FIN scan sends FIN packets to probe the state of ports but does not establish a connection; an ACK scan is primarily used for mapping firewalls and understanding how they respond to packets; and a Null scan sends packets without any flags set, which can be used to identify open ports based on the responses received. However, none of these techniques establish a full connection like the TCP connect scan does.