Did you know that when your WiFi is on, you broadcast a lot of information about your phone and what access points it knows out into the ether as it scans and attempts to connect to any device it previously has? Even with background scanning available you’re still broadcasting to anyone tracking WiFi that you’re around.
That at least is the claim of Pry-Fi for root users. I’m actually a little out of my field of security knowledge on broadcasting SSIDs to connect to SSIDs, so I’ll have to trust what the developer says when he says you can hide a tracker near someone’s house and get a reliable schedule of their comings and goings.
A malicious deactivated cell phone with only WiFi scanning turned on could sit and sniff for nearly a month before needing to be picked up for recharge and log retrieval.
Pry-Fi works by hiding the list of WiFi access points you know from broadcast and when you’re connecting to a WiFi access point it randomizes your MAC address so that, although you’re connected and connectable, there’s no way someone who’s snooping is going to know that you’re the same person who connected before. You look like a new device that just joined a network.
The writeup on stores tracking your movements via cell phone in the support thread for the app is worth a read and kind of spooky since I just went to Walmart for the first time in forever and then got a survey asking if I had just been to Walmart. Although it could be coincidence, and probably is, I feel I’d like to not be trackable via cell phone within a store that can figure out who I am based on paying with a credit card and position within the store.
While Pry-Fi is free and an uninstallable application, you might want to go ahead and make a nandroid backup just in case there are any issues with how it handles your WiFi. It’ll even suggest that if you select MAC spoofing while connected.
Pry-Fi isn’t for every phone, and doesn’t seem as though it’s been touched much in the past few months it does seem as though it’s actively supported so it’s probably worth a look if you’re feeling like stopping being as easily trackable. It’s also by a fairly well known developer, if you feel uneasy about root apps by unknowns.
Alternately, you can disable background WiFi scanning when you’re out and about.