WiFi & Bluetooth Hygiene
Your phone broadcasts a history of every network it's ever connected to. Shops track your movement via Bluetooth. Here's how to stop both.
What's Actually Happening
Every time your phone's WiFi is on and not connected, it broadcasts "probe requests": asking for every network it's ever remembered. This list is unique to you and can be read by anyone with basic equipment. Shops, airports, and surveillance firms use this to track you.
Retailers place Bluetooth beacons throughout stores. Your phone's Bluetooth address is read as you walk past each one: mapping your movement through the store and correlating it with your purchase data. Some systems link this to your loyalty card identity.
Public WiFi operators can see all unencrypted traffic. Many capture your device's MAC address for tracking. Free WiFi that requires an email address is a data collection operation. Your device can be impersonated by a rogue access point with the same network name.
Modern iOS and Android randomise your MAC address per network by default: but this is sometimes disabled or bypassed. Ensuring it's on prevents your device being tracked across different WiFi networks even without connecting.