Which option corresponds to a UDP scan in hping3?

Which option corresponds to a UDP scan in hping3?

• A. -2 (UDP scan)
• B. -A (ACK scan)
• C. -S (SYN scan)
• D. -1 (ICMP ping)

Answer: (A)

UDP scanning in hping3 is performed by using the -2 flag. This mode sends UDP packets to the target ports and watches how the host responds or whether there is no response at all. Because UDP is connectionless, many devices don’t reply to those probes. When a port is closed, you often get an ICMP Port Unreachable response; when a port is open, you may get no reply or a different firewall-related response, and filtered ports may also produce little to no reply. This behavior lets you infer port states based on the presence or absence of responses. The other common scan modes use different flags: the ACK scan mode is triggered by its specific flag and sends TCP ACK packets to probe how the host handles them; the SYN scan mode uses its own flag and sends SYN packets to observe SYN-ACK or RST replies to determine open ports; and the ICMP ping flag sends ICMP Echo requests to check whether the host is reachable, not to scan ports.

UDP scanning in hping3 is performed by using the -2 flag. This mode sends UDP packets to the target ports and watches how the host responds or whether there is no response at all. Because UDP is connectionless, many devices don’t reply to those probes. When a port is closed, you often get an ICMP Port Unreachable response; when a port is open, you may get no reply or a different firewall-related response, and filtered ports may also produce little to no reply. This behavior lets you infer port states based on the presence or absence of responses.

The other common scan modes use different flags: the ACK scan mode is triggered by its specific flag and sends TCP ACK packets to probe how the host handles them; the SYN scan mode uses its own flag and sends SYN packets to observe SYN-ACK or RST replies to determine open ports; and the ICMP ping flag sends ICMP Echo requests to check whether the host is reachable, not to scan ports.