iOS 7 will contain a blacklist system that allows blocking of calls or messages

  In the whole suite of interesting news from iOS 7, we also include a blacklist system about which Apple has not said anything. In the image showing the APIs that developers will be able to use for applications, those from Apple included an API that allows blocking FaceTime calls, voice and iMessage messages, but unfortunately did not provide any details for they. We are probably talking about a blacklist system that will allow us to block calls or messages received from our contacts, but it remains to be seen if everything will work with unknown numbers.