What does 6667/tcp filtered irc mean in nmap scan?

Question

Information Security

Hello. I started a small VPS server for various test purposes - a couple of sites are spinning there, and something else. Yesterday I flashed my home router from stock firmware to OpenWRT. I set up and decided to scan the router with VPS using nmap, from the outside. IP white, static. And I was surprised that, in addition to the ports that I obviously open and need, there is no mention of this port in the list of open ones
6667/tcp filtered irc
. In /etc/config/firewall there is no mention of this port. Google did not give anything intelligible, all links to the IRC setting, which I do not have and do not need. What can all this mean?

Answer 1

Possibly False-Positive (Wrong decision).
Filtered means that a firewall, filter, or something else on the network is blocking the port so that Nmap cannot tell if the port is open or closed.
Try adding the --reason option when scanning, it will display the reason why the decision was made on the port. As an option, try other scanning modes (sT, for example).
More details about scanning modes: https://nmap.org/man/en/man-port-scanning-techniqu...
Connect to the router via SSH and enter the netstat -atnp command. Will list the ports in use and the applications that use the port.