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This post describes my UFW config and is here so I find it from somewhere and with hope that I am told if someone notices something terriby insecure here and is able to offer suggestions.

Having firewall is important as you aren’t always in your trusted home network and with IPv6 your devices have public IPv6 addresses.

This post first has list of commands, then explanations.

ufw limit 22/tcp
ufw default deny incoming
ufw default allow outgoing
systemctl enable ufw && systemctl start ufw
ufw enable
ufw reject 113/tcp
ufw allow from 172.16.0.0/16 to any port 631
ufw allow 3544/udp
ufw allow from 172.16.0.0/16 to any port 5353 proto udp
ufw allow from 173.16.0.0/16 to any port 9091 proto tcp
ufw allow from 172.16.0.0/16 to any port 17500 proto tcp
ufw allow 60000:61000/udp
  • 22 TCP/ssh — Prevent more than 6 connections in 30 seconds to the SSH port and it’s the first command as you don’t want to lock yourself out of it.
  • Deny incoming connections unless the port has been whitelisted.
  • Allow all outgoing connections, keeping list of authorized ports would be too much for me.
  • Start ufw on boot and now (I am not sure if this step is required, but better safe than sorry).
  • Put the firewall in force.
  • 113 TCP/ident — Tell “Connection refused” to whoever tries to reach port
    1. This makes ident checking IRC servers connect faster as they don’t have to timeout. If you run shell server (for IRC purpouses) you should allow this instead.
  • 631 both/cups — Allow access to cups for printer sharing from local network
  • 3544 udp/miredo — Sadly native IPv6 isn’t everywhere, neither is 6rd with every ISP or proper tunnel.
  • 5353 UDP/mdns/Avahi — used for .local addresses and probably not needed outside local network
  • 9091 TCP/transmission web interface — also something I want to access from LAN. This seems risky too, but risks can be limited by only using this rule with static hosts.
    • Transmission file transfer uses TCP. Default port: 51413.
  • 17500 TCP/Dropbox LAN sync — which I use with desktops
  • 60000:61000 UDP/mosh — I feel this is the most insecure part of this setup and there should be something bettter instead of this.

If some host doesn’t run some of the mentioned service, it’s not open in the firewall.