Progressive multi gray-leveling: a voice spam protection algorithm

As voice over IP gains popularity, it is easy to imagine that Internet hacking and other security problems we currently face with email spam will attack the VoIP environment. In contrast to email protocols represented by SMTP, VoIP does not tolerate any negotiation in its signaling steps or screening content due to the delay limitation. Thus, it is difficult to implement voice spam protection or control algorithms by just mimicking popular email spam protection algorithms. This article proposes a voice spam control algorithm called progressive multi gray-leveling (PMG) that fits in VoIP settings. PMG progressively calculates the "gray level" of a caller and determines whether the call will be connected or blocked based on previous call patterns. Based on experiments, it turns out that PMG can learn a spammer\´s calling pattern and block massive spam attacks from them effectively