Edward Snowden said on twitter.
I wouldn’t use WiFi at home, because global maps of every wireless access point’s unique ID—including yours—are free and constantly updated. I would use ethernet; yes, ethernet on a phone. I would deny network permissions to any app that doesn’t need it using an app firewall.
What is this global maps of every wireless access point? This is the first time I’ve heard of it, but I couldn’t find any information, so I’d appreciate it if you could tell me if you know.