Which port state indicates the port is being blocked or not reachable due to packet filtering, and probes do not reach the port?

Which port state indicates the port is being blocked or not reachable due to packet filtering, and probes do not reach the port?

• A. filtered
• B. open|filtered
• C. Closed
• D. unfiltered

Answer: (A)

When a port state is labeled filtered, it means a firewall or packet filter is blocking the probes, so no response reaches the scanner. Because there’s no reply, the tester cannot determine whether the port is actually open or closed. This is exactly what happens when the port is blocked or not reachable due to filtering—the probes never get through to the port. If the port were open, you’d see a response from a service; if it were closed, you’d typically get a reject or reset. Ambiguous cases where the results could be open or filtered are shown as open|filtered, not simply filtered. Similarly, unfiltered means the port is reachable and not filtered, but the exact state (open or closed) isn’t determined from the probe alone.

When a port state is labeled filtered, it means a firewall or packet filter is blocking the probes, so no response reaches the scanner. Because there’s no reply, the tester cannot determine whether the port is actually open or closed. This is exactly what happens when the port is blocked or not reachable due to filtering—the probes never get through to the port. If the port were open, you’d see a response from a service; if it were closed, you’d typically get a reject or reset. Ambiguous cases where the results could be open or filtered are shown as open|filtered, not simply filtered. Similarly, unfiltered means the port is reachable and not filtered, but the exact state (open or closed) isn’t determined from the probe alone.