A system and method for detecting spam across a social network using a spam detector is disclosed. The system comprises a post receiving module, a fingerprint generator, a fingerprint comparison module, fingerprint storage and a spam response module. A comment is received by the post receiving module and a fingerprint is generated by the fingerprint generator using the comments. The fingerprint is compared to other fingerprints previously generated and stored by the fingerprint comparison module. If the fingerprint matches any previously stored fingerprints, it is assumed to be spam and processed accordingly by a spam response module. If the fingerprint does not match any previously stored fingerprints, it is posted in the social network.