The best advice for dealing with loan sharks is, well, don’t. But if you’re already in over your head you might want to ditch your phone.

Chinese police have uncovered an app that illegally collects location data to help debt collectors track down their debtors. The app, called App Detective, was frighteningly cheap and easy to use: Download it, register, and pay a minimum of 15 US cents to find the person who owes you money. (The leg breaking part is up to you.)

Nanjing city police said that the location accuracy was quite good: The error margin was 20-50 meters. The police found out about it in January 2018, when one of the debtors, caught by his loan sharks in the middle of lunch, came to report the case to the police. However, the case was not made public until this year. Two app operators were handed over to the prosecution, media reported on Friday.

The most prized tool for loan sharks is no longer a baseball bat. (Picture: Jiangsu Police official WeChat account)

We don’t know exactly how it works, but a preliminary police investigation found that App Detective collects real-time location data from mainstream chat apps.

“By cracking the security protection system of chat applications, it intruded into and illegally obtained latitude and longitude information of the target, thus illegally obtained the specific location of a person,” Yang Guinian, deputy commander of the Internet Security Department of the Nanjing Police Gulou branch was quoted saying in a statement published on Jiangsu police official WeChat account.

According to Chinese law, obtaining the location of users is not allowed without permission (except in certain legal situations).

But, as most of us know, apps are known to collect location and other data without our knowledge. The International Computer Science Institute published a report this week saying that roughly 17,000 Android apps collect identifying information, data that’s usually sold to advertisers. But as the many data leak scandals uncovered in China this year show, this data can easily end up in the wrong hands.

That’s not the only issue. It’s not that hard to find apps that can track down your location perfectly legally without your knowledge.

A quick search on Google will give you leads like Five Apps for Spying on Your Spouse (not creepy at all) and a Quora question on how to track your (presumably cheating) husband. If you're close enough with a person to know their iCloud or Google account you can track them through the platform -- provided that they turn location services on.

The App Detective, however, seems to have been popular in more, uh, professional settings. The app was not only used among individuals, but also 80 investigative and debt collecting companies for tracking targets. More sophisticated types of tracking across multiple chat apps could cost around US$15. By the time this case was publicized, the app had 4,000 registered users and made more than US$59,000.

But if you’re on the lookout for even more shadier methods for tracking, look no further than Chinese ecommerce sites, which are full of cheap equipment to spy on people.