Hashing IPs is ineffective, the IP namespace is so small a rainbow table (or even brute force) would be trivial so effectively the hash of an I is identical to

Hashing IPs is ineffective, the IP namespace is so small a rainbow table (or even brute force) would be trivial so effectively the hash of an I is identical to the IP itself. Unless you salt it but if you do that it becomes useless for analytical, fraud prevention, and security purposes. Same goes for credit card numbers, as an aside, I saw a credit card number being hashed in an app I was consulting on once... don't do that. Rainbow tables are stupid simple on inputs that small.