If a target machine sends back RESETs or ICMP Port Unreachable, what happens?

• A. The results will be encrypted
• B. The scan will be unable to proceed
• C. The target is immune
• D. The scan can occur more quickly because we don't have to wait for a timeout

Answer: (D)

When probing ports, you rely on responses to determine state. A TCP reset means the port is closed, and an ICMP Port Unreachable from a UDP probe also indicates a closed port. These definitive replies tell you immediately that the port isn’t open, so you don’t have to wait for a timeout to conclude its state. That lets the scan move on faster, reducing overall time.

The other options don’t fit because a reset or ICMP unreachable doesn’t encrypt results, doesn’t make the scan unable to proceed, and doesn’t imply immunity—just a closed port. The key benefit here is the ability to skip waiting for timeouts when a definitive negative response is received.