8 Ways You Can Be Tracked While Paying with Cash

If you think you're off the grid when you pay cash (versus a credit card), think again. You're leaving far more digital breadcrumbs than you realize.

Dollar bill
Credit: Kuzma

People who place a high premium on privacy—and who simply don't want to tracked at all, let alone while shopping—often think they can be invisible to marketers (and everyone else) by paying cash and never using a loyalty card. Alas, in 2014, keeping a low profile isn't nearly that easy. If marketers or law enforcement want to track you, they have many ways to do it. When grocery shopping for a loaf of bread, you're likely leaving far more digital breadcrumb trails than you realize.

Security cameras
Security camera

What: Those store security cameras can do a lot more than identify known shoplifters. Using facial recognition software coupled with access to social media images, the ability to identify shoppers is real.

Deployment: One convenience chain has already fessed up to using such facial recognition to determine the ads shown in digital media, but many more are experimenting in the field. A camera watches someone come in and has a tentative ID based on facial recognition. It can then compile a list of everything that shopper does — by name.

Protection: None. Unless the store chooses to send you a sales pitch, no opt-in is needed.

Shopper loading car
License plate

What: So you're driving into your neighborhood shopping center, all prepared to do some incognito retailing, and you're identified before you even leave your car. More precisely, your car is what has been identified. But it doesn't take long to find your name associated with that license plate. If third-parties databases are coordinated, every parking lot you drive into — and every store you walk into — can be tracked.

Deployment: The data being captured is widespread. How many retailers are actively using the data is undetermined, but the number will clearly increase.

Protection: None.

Free Wi-Fi
Free Wi-Fi

What: If the phone's identification is grabbed, tracking shall commence.

Deployment: Nordstrom last year counted customers through their mobile signals. It gets worse: The vendor they were using for its mobile trial was also running the program for at least 35 other of the nation's 100 largest retailers. This allowed the vendor to tell Nordstrom when a shopper was new or had been in the store 20 times. But it also knew everything that shopper did at every one of the stores he worked with.

Protection: Leave phone or tablet on airplane mode and definitely off of the store's Wi-Fi. Better yet, turn it off. 

Mobile coupon
Mobile coupons

What: Beyond the store's Wi-Fi detecting when you've logged in, there are many ways for your mobile device to be tracked.

Deployment: Macy's found a very cost-effective way to allow customers to get points for checking into the store. It piggybacked on its decades-old audio speaker system. The same units that inundate you with elevator music send out high-frequency sounds that the mobile device's app looks for. By listening for the signal strength between multiple speakers, it can triangulate your exact location—and then track you.

Protection: Turn phone off. 

Earth's magnetic field
Earth's magnetic field

What: Some stores are leveraging the earth's magnetic field to locate you near any aisle.

Deployment: A Finland company, working with major retailers, can track where you and your activated mobile device are within four inches, thanks to gravity. “Steel masses inside buildings twist Mother Earth's magnetic field such that every spot produces a unique pattern. Each building, floor and corridor creates a distinct magnetic field disturbance that can be measured to identify a location and generate a map," is how the vendor describes it.

Protection: Turn phone off. If your phone's on and you're not aboard the space shuttle, you're going to be found. 


What: The normal defensive technique of going into airplane mode and switching off Wi-Fi will halt most mobile detection systems. But one approach can find you another: through Bluetooth.

Deployment: One retail mobile tracking company, LoyalBlocks, is using Apple's Beacon system to detect any phone — even in airplane mode, with Wi-Fi turned off — if its Bluetooth is enabled. Once detected, it can identify the phone and you. It could also track Bluetooth before Apple's Beacon, but Beacon makes it even easier.

Protection: Turn phone off. 

Driver's license
Driver's license

What: Let's say you made a purchase in cash and now you want to return the item. Whether or not you have the receipt, many retailers today will insist seeing your driver's license. There is a legitimate reason: many thieves use returns as a way to launder—or monetize--stolen merchandise. But they also want to discourage people from returning very often, so many will use a service that counts how often you process returns.

Deployment: Most major chains are using a system to track returns. The problem: There are no current restrictions as to how the chains can use your driver's license information once they have it.

Protection: Shop in stores that don't require a driver's license and won't limit returns. 

Mobile app
Credit: ByteLight
LED lighbulbs

What: Another way that phones can be tracked when they are in airplane mode and off of Wi-Fi is, believe it or not, through specially enhanced LED bulbs. The bulb sends out an unusual light pattern that an app on the phone recognizes. The strength of the received pattern indicates where the shopper is standing within one meter when it's triangulated with patterns from nearby lights.

Deployment: Some retailers in China have been using this along with the Boston Museum of Science and unspecified U.S. chains.

Protection: Keep the phone buried in your pocket or purse where it can't detect the light.