IT vendor NEC will debut technology at next month’s 3GSM World Congress in Barcelona that is designed to block spam over internet telephony, or SPIT.

Called VoIP SEAL, the system works by being able to detect who is making the incoming call by applying the Turing test to the system making the call. If the algorithms decide the caller is non-human then the system blocks the call, stopping the user’s phone from ringing.

An important feature of the technology is that the system will eventually have the capability to be customised to work with home network kit, telco carrier session border controllers and session initiation protocol (SIP) hardware.

Because SIP was designed for native 'presence' support, SPIT programmers could check your availability before SPITing on you. NEC say that they have simulated SPIT attacks conducted through botnets, 99 percent of which were stopped using VoIP SEAL. No date was supplied for a commercial release of the software.