An anonymous reader writes: British telco BT is launching a free landline service for UK customers which promises to divert millions of unwanted calls. A dedicated team at BT will monitor calls made to UK numbers, across its network of over 10 million domestic landlines, to identify suspicious patterns, which could help to filter out nuisance callers. The flagged numbers will then be directed to a junk voicemail box. The company has estimated that the voicemail 'net' will catch up to 25 million cold calls every week. It explained that to achieve this success rate, it would be deploying enormous amounts of compute power to monitor and analyse large amounts of data in real-time.