Like everyone else these days, we’re weary of spam calls on our mobile phone (and we’re sure landlines must be getting them too, if anyone still has a landline these days). Calls from the IRS (would they really call my cell?), that latest dream vacation (the one place I can guarantee you that we would NEVER go is the place that deceitfully calls our phone asking for Sarah, then says in the recording, “Oh, ok, well you’ll do,” and many others are badgering and nagging us, using up our time, breaking our concentration, and in general, just annoying us. But we remain unconvinced that Truecaller is a true solution. If you wondered, just observe the squabble at…

https://www.quora.com/How-safe-is-Truecaller

Some reviewers point to the fact that we would need to reveal our entire list of contacts and calls to the app, which is, in a sense, compiling all these things into a huge reverse-engineered active cell phone directory that could then be sold (someday?) to the highest bidder or even broken (scammed) itself and used by bad guys. Bottom line: Better think twice (or three times) before buying into it, especially if you have contacts working in sensitive places on that contact list of yours. Oops.