Loopback Address
A loopback address is a reserved IP address that sends outgoing signals back to the same computer for testing.
IPv4
127.0.0.1 though it is often represented as localhost.
IPv6
0000:0000:0000:0000:0000:0000:0000:0001 and its permutations.
Regex
A good regex to filter those loopback addresses out:
^localhost$|^127(?:\.[0-9]+){0,2}\.[0-9]+$|^(?:0*\:)*?:?0*1$