Retailers Tracking Your Cell Phone Signals

Shoppers know there’s a trade-off involved in signing up for a retailer’s loyalty program or app: discounts and rewards in exchange for information about you and your buying habits. But simply browsing in a store with your cell phone in your pocket can be almost as revealing. That’s because when a phone scans for nearby wireless networks or Bluetooth signals, it emits a unique code, called a MAC (media access control) address. Companies can read the string of characters and zero in on your movements.

How to Keep Your Data Private

This mobile eavesdropping is more widespread than you might think, says Pam Dixon, executive director of the World Privacy Forum. Most retailers are mum about tracking, but the practice is more common among those with multiple locations, she says.

Retailers say the information helps improve store layout, schedule staff efficiently and shorten lines. Analytics firms that shadow these signals say your ID is protected because data is anonymous, aggregated with data from other shoppers, or both. But privacy advocates say that even without knowing a cell phone owner’s name, analysts can infer lifestyle interests based on how long shoppers linger in an aisle or how often they visit a location, and can trace these patterns for years.

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You can limit tracking by registering your MAC address with the Future of Privacy Forum’s new opt-out platform at www.smartstoreprivacy.org. Unfortunately, doing so will remove your identifier only from the handful of companies that have agreed to comply. A better fix: disabling Wi-Fi and Bluetooth while shopping. And iPhone users may be pleased with a privacy-friendly feature of iOS 8, expected this fall, that broadcasts randomized MAC addresses to cover the user’s trail.

Miriam lived in Toronto, Canada, before joining Kiplinger's Personal Finance in November 2012. Prior to that, she freelanced as a fact-checker for several Canadian publications, including Reader's Digest Canada, Style at Home and Air Canada's enRoute. She received a BA from the University of Toronto with a major in English literature and completed a certificate in Magazine and Web Publishing at Ryerson University.