A UDP scan on port 80 checks for what?

A UDP scan on port 80 checks for what?

• A. Whether a UDP Service Responds on Port 80
• B. Whether a UDP Service on Port 80 is Blocked by a Firewall
• C. Whether Port 80 Supports TCP
• D. Whether the Host Responds to DNS Queries

Answer: (A)

A UDP scan to a port is used to determine if a UDP service is listening on that port by sending a UDP packet and observing any response. Since UDP is connectionless and has no handshake, there isn’t a guaranteed acknowledgment back, but a UDP service that is active might reply, or the host may respond with an ICMP Port Unreachable if the port is closed. The key idea is to discover whether anything usable speaks UDP on that port, rather than whether TCP is involved or whether the port handles DNS queries. On port 80, which is typically used for HTTP over TCP, the question tests the idea of detecting a UDP service’s presence by observing a response to a UDP probe. If there’s no response, the port could be closed, filtered by a firewall, or simply not running a UDP service. So the best takeaway is that a UDP scan checks whether a UDP service responds on that port.

A UDP scan to a port is used to determine if a UDP service is listening on that port by sending a UDP packet and observing any response. Since UDP is connectionless and has no handshake, there isn’t a guaranteed acknowledgment back, but a UDP service that is active might reply, or the host may respond with an ICMP Port Unreachable if the port is closed. The key idea is to discover whether anything usable speaks UDP on that port, rather than whether TCP is involved or whether the port handles DNS queries. On port 80, which is typically used for HTTP over TCP, the question tests the idea of detecting a UDP service’s presence by observing a response to a UDP probe. If there’s no response, the port could be closed, filtered by a firewall, or simply not running a UDP service. So the best takeaway is that a UDP scan checks whether a UDP service responds on that port.