The --open option shows which port states?

• A. Open ports only
• B. Open, open|filtered, and unfiltered ports
• C. All ports including closed
• D. Closed ports only

Answer: (B)

The option controls which port states are shown in the results, filtering out clearly closed ports and focusing on ports that are not definitively closed. In Nmap’s terminology, a port can be open, open|filtered (ambiguous due to a firewall), or unfiltered (reachable but not clearly open or closed). Using this filter means you’ll see ports that are truly open, potentially open (open|filtered), or accessible (unfiltered), while closed ports disappear from the list. That’s why the correct choice lists open, open|filtered, and unfiltered ports.