How do advertisers always know where you are?

2 min read
Lexie

Hi, I'm Lexie! I write about information security, Bitcoin, and privacy.

A pigeon with a pair of binoculars.

To build a profile of you, advertisers can gather a multitude of information. They can follow you around the web using a tracking code, browser fingerprinting, store cookies on your machine, or even buy your credit card data.

But advertisers can also follow your physical location: Bluetooth beacons around cities and malls can track your movements, and Google can use your IP address to locate you—even when you’re not sharing your location.

Rule 1: Turn off location sharing

The most trivial way for an advertiser to learn your location is for your device to tell them.

Protect yourself: Make sure that your device’s operating system, apps, and browser have all location sharing features turned off.

Bluetooth beacons are watching you

These small physical devices are hidden in supermarket shelves, advertising posters, and malls. They continuously broadcast a signal that some of your phone’s apps can pick up. Similar to a cookie on the web, the beacons tell your app that you have visited a place or walked past an advertisement.

This information allows the advertisers to track your movements, as well as which ads or products you have seen or inspected. Beacons are primarily used to measure the effectiveness of marketing techniques and serve you more targeted ads.

Protect yourself: Turn off bluetooth and avoid applications known to engage in this behavior, such as Facebook.

IP Addresses give up your location

IP addresses can geo-locate your position and serve you ads. To determine your physical location, advertisers such as Google rely on a small portion of the population sharing their device’s GPS location. The devices will then associate this location with the IP address of your network, such as the coffee shop or office you are currently in.

This makes it possible to know the location of all subsequent users of the same network. Even if they carefully avoid sharing their location. It only takes one negligent visitor to associate your home IP with your physical location, then all sites you visit in the future will know where you reside.

Protect yourself: Always keep your VPN turned on, and route highly sensitive data through Tor.

Mobile towers can triangulate your location

As you move around, your device is always connected to two or more cell phone towers, so your cell phone provider can always calculate your location. This information can then be sold to advertisers, as major providers have done in the past.

Protect yourself: Choose a privacy-conscious ISP, always keep your VPN turned on, and route highly sensitive data through Tor.

Exercise caution, wherever you are

Simply turning location features off is not enough. Be mindful of exposing your IP address, picking up the signal of Bluetooth beacons or ISPs that sell your location data.

Lexie is the blog's resident tech expert and gets excited about empowerment through technology, space travel, and pancakes with blueberries.