From Find My Phone services, to Life360 for your friends and family, to allowing certain apps like Maps to see where you are, there are a million reasons why people turn on location services. It’s a quick and convenient way to make sure your loved ones are safe, while simultaneously getting geographically relevant information about where you are and what there is to do nearby.

Would you be surprised to learn there is a dark side to location sharing?

Many companies use location data to build detailed user profiles. This information includes not just where you live, but also the places you frequent, the routes you take, and how often you visit certain locations.

As soon as you allow apps and services to store your location data, you open yourself up to the risk of being followed—virtually or physically. These apps can be hacked, leaking your information to cybercriminals who go after data like this because it can be quite lucrative on the dark marketplace. Location data is very valuable, especially when combined with other personal details. Cybercriminals can use your location data to craft more convincing phishing attempts, for example. Imagine getting a message about a suspicious activity on your bank account when you’re on vacation; it’s much more convincing because the attacker knows exactly when and where you are visiting.

That’s not to mention the third parties with whom these apps explicitly share their data. Because many apps collect location data beyond what’s strictly necessary for their function, they can sell a whole lot more than just information on what you’re browsing. When this data is sold to third-party brokers, as it often is to bring down the application’s cost of operating, these brokers can then use your location information to build a profile on you, including your habits, routines, and frequented locations. Who wants to give that much away to unknown entities?

This information can be used for targeted advertising, but it can also be sold to other companies, including those with less savory intentions. Even in the hands of a legitimate third party, your location can be used by advertisers to bombard you with unwanted spam relevant to where you’ve been. While this might seem harmless, it can feel intrusive and can be used to manipulate your purchasing decisions.

Some insurers are starting to consider location data when setting premiums. For example, if you frequent high-crime areas, your insurance rates might go up.

Letting people know exactly where you are can expose you to potential dangers. This could be a thief knowing your house is empty or someone following you after leaving a bar alone at night. Sharing your location, especially frequently or in real-time, can make you vulnerable to stalkers—whether it’s a stranger who hacked your phone or someone with whom you willingly shared your location!

Think you can leave your phone at home and avoid these risks? Not necessarily. Fitness trackers or apps that share your running routes can be risky as they create a predictable pattern of your movements. Even if the information isn’t being misused, constantly sharing your location allows friends and third parties to build a detailed picture of your life, like your home, work, favorite haunts, and routines.

The constant sharing of your location can also chip away at your sense of privacy. It normalizes constant surveillance and makes you less aware of (or even less concerned about) who might have access to your whereabouts.

Even seemingly innocuous location sharing, like geotagging photos on social media, can expose where you live, work out, or spend your free time. This information can be aggregated by third parties to build a detailed picture of your life. It can even be misused by trusted friends to physically endanger you!’

It’s important to keep all of this in mind when determining who can view your location and how much information they receive.