Abstract: A method obtains a first data item signature for a first data item, the first data item signature comprising an association between a plurality of synch points in the first data item and a corresponding plurality of block signatures. The process attempts to find one of the synch points in a second data item; and, if such a synch point is found, then a block signature of a corresponding block of bits in the second data item is determined. The process ascertains whether the synch point and corresponding block signature from the second data item correspond to a synch point and block signature in the first data item. If a predetermined number of synch points and corresponding block signatures match, the first and second data items are considered to match. In response to said determining, one or more actions associated with the first data item are performed.

Abstract: A method obtains a first data item signature for a first data item, the first data item signature comprising an association between a plurality of synch points in the first data item and a corresponding plurality of block signatures. The process attempts to find one of the plurality of synch points in a second data item; and, if such a synch point is found, then a block signature of a corresponding block of bits in the second data item is determined by applying a hash function to the corresponding block of bits in the second data item. The process ascertains whether the synch point and corresponding block signature from the second data item correspond to a synch point and block signature in the first data item signature. If a predetermined number of synch points and corresponding block signatures match, the first and second data items are considered to match.

Abstract: A filter for a distributed network may include receiving index requests from indexing nodes over a network and providing over the network index responses to the indexing nodes in response to the index requests. The index responses may instruct a receiving indexing node to index or not index a specified file. The method may be implemented in software and executed on a computer.