Which option would you use to perform a UDP scan?

Which option would you use to perform a UDP scan?

• A. -sS
• B. -sT
• C. -sU
• D. -sA

Answer: (C)

UDP scanning probes UDP ports because UDP is a connectionless protocol with no handshake. When you use the UDP scan switch, Nmap sends UDP packets to target ports and waits for responses. If a port replies with a UDP payload, it’s likely open. If you receive an ICMP Port Unreachable message, the port is closed. If there is no reply, the port is usually considered open|filtered, since a firewall or filtering device might be dropping the packets. This approach tends to be slower and noisier than TCP scans, and many hosts filter or rate-limit UDP traffic. Other common scanning methods target TCP behavior: one uses a SYN packet to elicit a half-open handshake, another attempts a full TCP connect, and another analyzes responses to ACK probes to infer firewall rules. The UDP switch is the appropriate choice when you specifically need to assess UDP ports.

UDP scanning probes UDP ports because UDP is a connectionless protocol with no handshake. When you use the UDP scan switch, Nmap sends UDP packets to target ports and waits for responses. If a port replies with a UDP payload, it’s likely open. If you receive an ICMP Port Unreachable message, the port is closed. If there is no reply, the port is usually considered open|filtered, since a firewall or filtering device might be dropping the packets. This approach tends to be slower and noisier than TCP scans, and many hosts filter or rate-limit UDP traffic.

Other common scanning methods target TCP behavior: one uses a SYN packet to elicit a half-open handshake, another attempts a full TCP connect, and another analyzes responses to ACK probes to infer firewall rules. The UDP switch is the appropriate choice when you specifically need to assess UDP ports.