Configure the loopback interface to accept traffic. Configure all other interfaces to deny traffic to the loopback network (127.0.0.0/8).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. FIX: Make sure iptables-persistent installed. If you are using iptables, # iptables -A INPUT -i lo -j ACCEPT # iptables -A OUTPUT -o lo -j ACCEPT # iptables -A INPUT -s 127.0.0.0/8 -j DROP or If you are using ufw, # ufw allow in on lo # ufw deny in from 127.0.0.0/8 # ufw deny in from ::1 # iptables-save > /etc/iptables/rules.v4 # ip6tables-save > /etc/iptables/rules.v6

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Run the following command: # ufw allow in on lo # ufw deny in from 127.0.0.0/8 # ufw deny in from ::1