Which scan type scans UDP ports?

Which scan type scans UDP ports?

• A. -sO
• B. -sP
• C. -sU
• D. -sS

Answer: (C)

UDP port scanning is done with the UDP scan mode (-sU). It sends UDP packets to target ports and uses the responses (or lack of responses) to determine port state. Because UDP is connectionless, there is no handshake, so open ports may simply ignore packets, and closed ports typically reply with an ICMP port-unreachable message. If there’s no reply or ICMP indicates filtering, the port is shown as open|filtered. This contrasts with TCP-focused scans like the SYN scan, which actively completes a TCP handshake to determine openness, and with scans that probe IP protocols or perform host discovery rather than port probing.

UDP port scanning is done with the UDP scan mode (-sU). It sends UDP packets to target ports and uses the responses (or lack of responses) to determine port state. Because UDP is connectionless, there is no handshake, so open ports may simply ignore packets, and closed ports typically reply with an ICMP port-unreachable message. If there’s no reply or ICMP indicates filtering, the port is shown as open|filtered. This contrasts with TCP-focused scans like the SYN scan, which actively completes a TCP handshake to determine openness, and with scans that probe IP protocols or perform host discovery rather than port probing.