US Patent 8141152 Method to detect spam over internet telephony (SPIT)

The present invention provides methods, devices, and systems for detecting and filtering SPam over Internet Telephony (SPIT). The invention includes a two level filter. The first level may include a robust audio hash used to filter audio messages based on their audio content and the second level may include a near-duplicate pattern matching algorithm having a number of content filters and an evaluator to aggregate the results from the multiple content filters. By supporting multiple aggregation methods, a more flexible SPIT detection scheme is provided.