What kind of auction should you never buy a phone from?

There are lots of auctions where you can get a new cellphone at a decent price, but apparently there’s one type that you should avoid. The devices sold at police auctions are reportedly not safe most of the time.

The Department of Computer Science at the University of Maryland recently did a study in which it purchased 228 phones from police auctions and then examined them to see if there was any data left on them. And while the police wipe these devices before sending them to auction, it turns out they don’t usually do the best job of it.

Of the 228 phones, the team was able to access all the data on 21.49 percent of them just by powering them on. Conversely, only 5.3 percent had all their data completely wiped. The rest had varying degrees of information still on them, most of which was relatively easy to locate without any advanced tech forensic skills or tools.

Some of that data was very sensitive, including things like emails, text messages, credit card details, banking information, Social Security numbers of identity theft victims and credit reports. From it, the team was able to determine that some of the devices had belonged to members of organized crime gangs, stalkers, sex workers and registered sex offenders.

“Our results show that a shocking amount of sensitive, personal information is easily accessible, even to a ‘low-effort’ adversary with no forensics expertise,” they said.