Eavesdropping on smartphone 13.56MHz NFC polling during screen wake-up/unlock

https://preview.redd.it/j7x2b1wbv6te1.png?width=1737&format=png&auto=webp&s=17b7e246b4cdc68f5d871af4e68427fb92669a81 While casually exploring the NFC frequency range using a software-defined radio, I stumbled upon something quite surprising for me. At first, I wasn’t sure what I was seeing — just random spikes in the part of the spectrum I was scanning for amateur voice comms. During one air raid alert (I am a resident of Ukraine), I observed a sudden spike in 4-ping short patterns on the spectrum. I googled the frequency and confirmed it was NFC (13.56MHz), which left me wondering what else could be sending long-range pings on that frequency. Then I picked up my phone and suddenly saw a huge spike with the same 4-ping pattern on the spectrum. I connected the dots, repeated the process, and suddenly understood what I was seeing. It was triggered by me tapping the screen. Presumably, I was seeing other people checking their iPhones for updates about incoming threats at night — and tho ... Read full article.