What is the initial action of a UDP port scan?

What is the initial action of a UDP port scan?

• A. Sent UDP Packet to every port
• B. -sU
• C. Open Response: A service responds with a UDP packet
• D. Close Response: ICMP port unreachable

Answer: (A)

UDP scans start by sending a UDP datagram to each target port. Since UDP is connectionless, there’s no handshake to establish first. What you get next depends on the port: an ICMP Port Unreachable may come back if a port is closed, a UDP reply might come from an open service, or you may get no reply at all if the port is filtered or the service doesn’t respond. The option to use UDP scan mode is a way to perform this type of probing, but the actual initial action is sending UDP packets to the ports.

UDP scans start by sending a UDP datagram to each target port. Since UDP is connectionless, there’s no handshake to establish first. What you get next depends on the port: an ICMP Port Unreachable may come back if a port is closed, a UDP reply might come from an open service, or you may get no reply at all if the port is filtered or the service doesn’t respond. The option to use UDP scan mode is a way to perform this type of probing, but the actual initial action is sending UDP packets to the ports.