Truecaller is likely one of the hottest caller ID apps on this planet and in some Asian and European nations, Truecaller is nearly inescapable. The app supplies an actual service. It blocks spam calls robotically out of your iPhone and tells you who is asking even when they aren’t in your cellphone e book. But on the flipside, which means that Truecaller has all of your private information. And it might seep into Truecaller’s database even for those who haven’t signed up for the service (because of the magic of crowdsourcing).