When apps ask for access to your address book and you consent, the data-sharing doesn't always stop there.
The names and contact information that used to stay safe in analog address books now float around the data economy, bouncing from smartphones to app-makers to third-party data collectors.
That means apps get the names and phone numbers of everyone in your contacts - from your best friend to the stranger who might have rear-ended you at a stoplight. And companies might sell that information, too.
There's no one-and-done option for turning off contact sharing, and the contacts you've already put out there are tough to take back. But if you'd like to start holding your address book closer to the vest, here's how.
Limit which apps access your address book.
On iOS, go to Settings -> Privacy -> Contacts and turn the slider to the off position on any apps you don't want access to the contacts stored on your iPhone.
On a recent Android phone, like the Samsung Galaxy S21, try Settings -> Privacy -> Permission Manager -> Contacts. See which apps are in the Allowed list, and remove permissions as needed.
Don't rush through app installations and sign-ups.
When that pop-up appears saying the app would like to access your contacts, be ready to hit "Don't Allow." In most cases, it won't affect the main features you use on the app. For some apps like messaging tools, it might make sense that they need your contacts to send and receive messages.
Change which third-party apps can see your Google and Microsoft account data.
First, go to Manage Your Google Account. On an Android, this is in your phone's Settings app under Google. On an iPhone, get there by opening any Google app, like Gmail, and tapping on your profile photo or icon in the upper right corner.
Scroll to the Security section and then down to Third Party Apps with Account Access. (This will only show up if there are apps accessing your account.) Under each app, there's a list of what information you've shared with it. Tap on an app, and hit Remove Access.
For Microsoft, log in at account.microsoft.com and click on the privacy tab at the top of the page. Under More Privacy Settings, find Apps and Services and go to View App Access Details. If you want to remove an app's access, select Edit and then Remove These Permissions.
Block apps from accessing your social media information.
Twitter: Open the Twitter phone app and tap on the three lines at the top left. Choose Settings and Privacy -> Account -> Apps and Sessions. That should bring up your connected apps. If you see any you don't want to share your Twitter connections with, tap on them and select Revoke App Permissions.
Facebook: On Facebook's app, tap on the three lines at the bottom right and choose Settings & Privacy -> Settings -> Apps and Websites. You can also turn off third-party app access altogether by hitting the Turn Off button under Apps, Websites and Games.
Adjust individual app settings.
If a particular app, like Venmo, is showing your contacts publicly and you want it to stop, go to the app's settings and check for a "private" option. On the Venmo app, that means tapping the three lines in the top right corner and scrolling down to Settings. Under Default Privacy Settings, choose private. Then, go to Friends List and set that to private, as well. You can even change all your past payments to private under Past Transactions.
Buy a burner phone.
Drastic? Perhaps. But if you really don't want to share your address book with apps - and whomever they sell that information to - buy a separate phone to store your contacts.
Send a data-deletion request.
If you're a California or Virginia resident, your state's privacy laws give you the right to ask companies to delete your personal data. In California, large app-makers and Internet companies are required to provide a toll-free number or email address where customers can submit data-deletion requests. Virginia's law requires companies to include instructions for sending requests in their publicly posted privacy policies.
If you live elsewhere, some companies will still honor your data-deletion request, as it's tough to confirm where each request comes from - not to mention bad customer service to people from states without proactive privacy legislation.
Set up an alternative phone number with Google Voice.
This app acts like a phone within your phone, with a separate number. If you give acquaintances the Voice number, your real phone number won't end up in app databases if those people share their contacts with apps.