US Patent 8085915 System and method for spam detection

A voice-over-internet protocol (VoIP) caller verification method includes generating a challenge to be sent to a VoIP caller which needs a response from the VoIP caller prior to accepting a VoIP call, wherein the challenge includes a test pattern crafted to create a greater load at a spammer VoIP caller as compared to a human VoIP caller. A response or lack thereof is determined from the VoIP caller, and the response is analyzed relative to an acceptable response to determine whether the VoIP caller is acceptable to communicate with.