VPN

Хорошая статья тут https://baks.dev/article/ubuntu/how-to-set-up-an-openvpn-server-on-ubuntu-18-04

Правила для IPTABLES

iptables -P FORWARD ACCEPT
iptables -t nat -A POSTROUTING -s 10.8.0.0/16 -o enp3s0 -j MASQUERADE
iptables -A INPUT -p tcp --destination-port 6881:6999 -j DROP
iptables -A OUTPUT -p tcp --source-port 6881:6999 -j DROP

https://www.linode.com/community/questions/5513/need-a-iptable-rule-to-disable-bittorrent