Vipul's Razor is a distributed, collaborative, spam detection and
filtering network. Razor establishes a distributed and constantly
updating catalogue of spam in propagation. This catalogue is used
by clients to filter out known spam. On receiving a spam, a Razor
Reporting Agent (run by an end-user or a troll box) calculates and
submits a 20-character unique identification of the spam (a SHA
Digest) to its closest Razor Catalogue Server. The Catalogue Server
echos this signature to other trusted servers after storing it in its
database. Prior to manual processing or transport-level reception,
Razor Filtering Agents (end-users and MTAs) check their incoming mail
against a Catalogue Server and filter out or deny transport in case of
a signature match. Catalogued spam, once identified and reported by
a Reporting Agent, can be blocked out by the rest of the Filtering
Agents on the network.