In an engineering paper, bunnie Huang and Ed Snowden describe a malware-resistant hardware Iphone privacy overlay
In July 2016, Andrew "bunnie" Huang and Edward Snowden presented their research on journalist-friendly mobile surveillance resistance at the first MIT Media Lab Forbidden Research conference; a little over a year later, they have published an extensive scholarly paper laying out the problems of detecting and interdicting malware in a mobile device, and presenting a gorgeously engineered hardware overlay that can be installed in an Iphone to physically monitor the networking components and report on their activity via a screen on a slim external case.
Huang is a legendary hardware engineer -- his 2017 book, "The Hardware Hacker" is absolutely the best book on the subject you will find. Snowden, of course, is the world's leading public authority on the surveillance capabilities and tactics of governments. Together, they are an unbeatable team.