ufw is the great command line app for managing iptables in Ubuntu. While any changes should use the ufw command, it is possible to rather manually edit user created ufw rules in cases where that might be desirable.
The file location is:
/lib/ufw/user.rules
For ipv6 rules, the file is:
/lib/ufw/user6.rules
As with iptables, rules are processed in the order of the file top to bottom. For example this first rule would be processed before the one following:
### tuple ### deny any any 0.0.0.0/0 any 192.168.1.1 in -A ufw-user-input -s 192.168.1.1 -j DROP ### tuple ### allow any 80 0.0.0.0/0 any 0.0.0.0/0 in -A ufw-user-input -p tcp --dport 80 -j ACCEPT
After making changes, restart ufw:
$ sudo service ufw restart
