People can look you up on Facebook using your phone number. Here’s how to stop them.

If you’ve ever given your phone number to Facebook, anyone can find your profile by running a Facebook search on that number. And we mean anyone with a Facebook account—not just your friends. Recently, a security researcher demonstrated that he could exploit Facebook by connecting hundreds of thousands of phone numbers with their owners’ names.

Even though Facebook lets anyone find you through a reverse phone number lookup by default, you can prevent it from happening by following these simple steps: 

Step 1: Log into your Facebook account.

Step 2: Go to Privacy Settings.

Step 3: On the Privacy Settings page, you’ll see a section for “How You Connect.” Click “edit settings” next to it.

Step 4: A box titled “How You Connect” will open. On the drop-down menu next to “Who can look you up using the email address or phone number you provided,” select “friends.” (This is as private as you can go; Facebook won’t let you limit it to “no one”).

Step 5:  Click the “Done” button to save your changes.

You’re done! Now you’ve limited Facebook’s reverse phone lookup so that only your friends can find you through your number. Unless it’s absolutely necessary, it’s a good idea to avoid giving your phone number to any social network, despite them repeatedly asking for it for “security purposes.”