Information
Configure the loopback interface to accept traffic. Configure all other interfaces to deny traffic to the loopback network (127.0.0.0/8).
Rationale:
Loopback traffic is generated between processes on machine and is typically critical to operation of the system. The loopback interface is the only place that loopback network (127.0.0.0/8) traffic should be seen, all other interfaces should ignore traffic on this network as an anti-spoofing measure.
Note: Changing firewall settings while connected over network can result in being locked out of the system.
Solution
Run the following commands to implement the loopback rules:
# nft add rule inet filter input iif lo accept
# nft create rule inet filter input ip saddr 127.0.0.0/8 counter drop
IF IPv6 is enabled:
Run the following command to implement the IPv6 loopback rules:
# nft add rule inet filter input ip6 saddr ::1 counter drop