1. A system for detecting whether a known content item is present in a plurality of unknown content items comprising: A first module adapted to receive known content and to generate known signatures from such known content; A database module operatively connected to the first receiving module adapted to store the generated known signatures in a database whereby each known signature is associated with a data value representing the identity of the known content; A matching module operatively connected to the database module that receives signatures derived from the unknown content, said received unknown signatures of the same type as the known signatures stored in the database and further adapted to determine by use of the database module whether the unknown content is the known content; and A remote receiving module that is adapted to receive unknown content, generate signatures from the unknown content of the same type as the signatures generated from the known content and transmit the generated unknown signatures to the matching module in order to cause the matching module to determine the identity of the unknown content.