filtered port means
Because I am courious why I got some filtered ports on my RedHat 9.0 :
Port State Service
21/tcp open ftp
22/tcp open ssh
25/tcp filtered smtp
80/tcp open http
135/tcp filtered loc-srv
139/tcp filtered netbios-ssn
445/tcp filtered microsoft-ds
1080/tcp filtered socks
2401/tcp open cvspserver
8080/tcp filtered http-proxy
