Below is the relevant piece of the manpage as shipped with 6.46. Everything below the <indexterm> node seems to be converted into a comment.
Cheers, -Hilko .PP .\" open port state open .RS 4 An application is actively accepting TCP connections, UDP datagrams or SCTP associations on this port\&. Finding these is often the primary goal of port scanning\&. Security\-minded people know that each open port is an avenue for attack\&. Attackers and pen\-testers want to exploit the open ports, while administrators try to close or protect them with firewalls without thwarting legitimate users\&. Open ports are also interesting for non\-security scans because they show services available for use on the network\&. .RE .PP .\" closed port state closed .RS 4 A closed port is accessible (it receives and responds to Nmap probe packets), but there is no application listening on it\&. They can be helpful in showing that a host is up on an IP address (host discovery, or ping scanning), and as part of OS detection\&. Because closed ports are reachable, it may be worth scanning later in case some open up\&. Administrators may want to consider blocking such ports with a firewall\&. Then they would appear in the filtered state, discussed next\&. .RE -- To UNSUBSCRIBE, email to debian-bugs-dist-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org
