I recently did a port scan (using www.ipfingerprints.com) on my Ubuntu 18.04 server and found a number of ports that I did not open. Here are the open ports:
PORT STATE SERVICE
22/tcp open ssh
25/tcp open smtp
80/tcp open http
111/tcp filtered rpcbind
135/tcp filtered msrpc
136/tcp filtered profile
137/tcp filtered netbios-ns
138/tcp filtered netbios-dgm
139/tcp filtered netbios-ssn
443/tcp open https
445/tcp filtered microsoft-ds
513/tcp filtered login
520/tcp filtered efs
Except for 22, 25, 80 and 443, I did not open the rest of these ports. Why are they open, and will it affect my server performance if I close all of these ports?
filtered
means they are blocked by a firewall.