I am trying to give better security to my Raspberry sever. When I installed UFW, I allowed just port 80/tcp and my own high port for SSH communication, and by default are all others ports "deny".
Then I scanned my server with nmap, and I found out that every UDP port is open. I don't know if I must close these ports, and if UDP ports are dangerous to me.
I just want to provide Web server and SSH.
Could I leave UDP ports open or not?
Why UFW has not close UDP ports at default settings if they are dangerous like TCP ?
Is enough if I block just INCOMING connections?