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.