UNIX for Dummies Questions & Answers

Hi,
Whenever I tried to run nmap on my linux (red hat 6.2) boxes i got these outputs:

4444/tcp filtered krb524
6666/tcp filtered irc-serv
6699/tcp filtered napster
8888/tcp filtered sun-answerbook

Can anybody please explain me what are those supposed to mean? Especially 'irc-serv' and 'napster' are making me unconfortable.
Thanks!

you just portscanned yourself and that showed which ports are opened (in your case filtered)...
irc-serv is simply an irc-server

since I've never used napster (yes!) I can't really say what that napster port is used for

All that means is that something is listening on that port, and the service (napster etc) is the service that is typicall associated with that port. You can ofter check you /etc/inetd.conf file to find some of these services.

But I can't find those services in my /etc/inetd.conf, /etc/services, /etc/xinet.conf files. Am I forgetting some other files to check? And what does the state "filtered" mean?
Thanks for all the replies!

There has to be a process listening on that port. I think you can use netstat to determine what they are, but am not sure.

Filtered means that there is some type of firewall software (IP Chains, IP Tables, IP Filter etc.) that is "filtering" the packets through that port. If you can't figure out what is listening on the port, close it with the fireall.

Actually, filtered means it has been through a firewall, and rather than rejecting the packet (sending it back), it simply drops it (ignores it). When nmap doesn't get a responce back at all, it assumes it's been dropped by a firewall, thus "filtered". Otherwise it would show as closed (got a reset response) or open (got a favorable response, like a syn-ack).
If you're really worried, try using netstat or lsof to determine which ports are open.

I did 'netstat' but i can't find any of these ports being listened. And my machines are neither behind firewall nor running any firewall software. That's whats worries me since their services won't work behind firewall, due to dynamic UDP port usage.