Any time you walk into your average retail store, they are keeping tabs on you. You don’t have a rent-a-cop tailing you. It’s the store’s Wi-Fi and its accomplice, your smartphone. But you can keep it from happening with a little knowledge of how it works.

It’s a frightening thought that stores are tracking your location down to the display you are standing in front of at all times upon entering the premises. When your Wi-Fi is switched to the on setting, it is constantly searching for a signal. This allows sensors placed in displays around the store to follow you around. By the way, they know more than just that “someone” is there. Your phone’s wireless adapter has a unique address. They know the exact location of the device and who it belongs to.

What is the system keeping tabs on? Things like how frequently you enter the building, where you go when you are there and how long you spend shopping at that location. Video surveillance allows them to add more information to the data they have on you, such as gender, race and a rough estimate of your age.

We’re no strangers to having data collected on us. Stores get the same kind of info from us when we visit their online stores. Of course, we can read the privacy policy there. In store, they leave out the fine print.

Of course, there are potential benefits. Such data gives stores the opportunity to tailor your shopping experience to what you want and need most. On the other hand, there are clear privacy concerns. So what if you want to “opt out”? There’s one simple solution. When you leave your house, shut the Wi-Fi adapter off on all of your mobile devices. Without that turned on, there’s nothing for the store’s Wi-Fi to keep track of.