Your Contacts Are a Treasure Trove of Personal Data
The contacts on your phone hold the numbers of a great many people - friends, family, teachers at school, the place where you work part-time. That information is not yours alone; it is other people's personal data as well.
Should your contacts leak, the trouble may fall not only on you but on every single person listed in them. Managing your contacts properly is a matter of protecting yourself and the people around you. Phone number privacy is a question that involves not just your own number but the numbers of everybody else saved in your contacts.
Check Which Apps Can Read Your Contacts
When you install an app, you are sometimes asked whether to allow it access to your contacts. Do you tap Allow without giving it a thought?
Grant an app access to your contacts and it can read the name and phone number of every person listed there. Grant it to an app you cannot trust and your contacts may be sent to an outside server and used as a distribution list for nuisance calls and for sales calls that slip past a spam filter. Understanding how personal information leaks out of a phone number makes these decisions easier.
Apps it is reasonable to allow
- Phone apps and messaging apps, LINE and email among them
- Apps whose purpose is managing your contacts
Apps there is no need to allow
- Games
- Camera and photo-editing apps
- Weather apps
- Torch apps
- QR code readers
When an app with nothing to do with contacts asks for access to them, choose Don't Allow. Some apps ask for access in order to offer an invite-your-friends feature, but if you are not going to use it there is no need to grant anything.
How to check on an iPhone
- Go to Settings, then Privacy and Security, then Contacts
- A list of the apps that can reach your contacts appears
- Turn off the switch for any app that does not need it
The iPhone also has an App Privacy Report, which shows a history of the data each app has reached over the past seven days. Turn it on under Settings, then Privacy and Security, then App Privacy Report, and you can see at a glance which apps have been reading your contacts.
How to check on Android
- Go to Settings, then Apps, and choose the app you want to check
- Go to Permissions and check the Contacts setting
- Alternatively, go to Settings, then Privacy, then Permission manager, then Contacts
Android has a Privacy Dashboard, which shows a history of the permissions apps have used over the past 24 hours. You will find it under Settings, then Privacy, then Privacy Dashboard.
Check Your Cloud Sync Settings
The contacts on your phone are, more often than not, synced - backed up - automatically to a Google account or to iCloud. That is a useful feature in itself, but if the account is hijacked your contacts leak with it.
- Make the password on your Google account or Apple ID a strong one: 12 characters or more, mixing letters, numbers and symbols
- Set up two-factor authentication, preferably using an authenticator app
- Sign out on any device you no longer use
- Check your sign-in history from time to time, looking for access you cannot account for
A Google account matters especially, because it is tied to a long list of services - Gmail, Google Drive, YouTube - so the consequences of a hijacking are correspondingly large. Never reuse a password. It is also reassuring to read up in advance on what to do if you lose your phone.
Beware of Suspicious Apps
Among the apps that advertise free phone-number lookups or nuisance-call blocking, there are some that harvest your contacts and send them elsewhere. Apps of this kind suck up the numbers of everybody in your contacts and accumulate them in a database of their own.
- Check the app store rating and the reviews - not just the number of stars, but what the reviews actually say
- Check whether the developer is a company you can trust
- Avoid apps with an unusually small number of downloads
- Avoid apps that ask for too many permissions; a torch app asking for your contacts is plainly out of order
- Read the app's privacy policy and check whether it says anything about providing data to third parties
Since the call blocking built into your phone is perfectly adequate on its own, there is no need to rely on a suspicious third-party app at all.
Do Not Give Out a Friend's Number Without Asking
Before you give a friend's phone number to somebody else, always get the friend's permission. Even when you are asked directly for so-and-so's number, good manners mean checking with them first.
This is not merely a question of manners; it matters from the point of view of protecting personal data as well. Giving a friend's number to a third party without asking is an intrusion on that friend's privacy. Should the number you passed on be misused, you may find yourself held responsible too.
Tidy Your Contacts Regularly
The more people there are in your contacts, the wider the damage if they leak. Go through your contacts from time to time and delete the details of anybody you are no longer in touch with.
- Consider deleting anybody you have not been in contact with for six months or more
- Delete temporary contacts, such as a delivery firm or a repair company, once the business is finished
- Back up the contacts that matter to the cloud before you start tidying
The Contacts Risk When You Lose Your Phone
If you drop your phone or it is stolen and you have not set a screen lock, anybody at all can reach your contacts. The chance that whoever picks it up will misuse those contacts to make fraud calls to your friends and family is not zero.
Always set a screen lock, whether a passcode, a fingerprint or face recognition. In the event that you do lose your phone, the iPhone's Find My feature and Android's Find My Device can lock it remotely or erase the data. Setting a PIN code on the SIM card as well guards against the risk of the SIM being taken out and used in another handset.
Summary
The contacts on your phone are personal data belonging not only to you but to everybody listed in them. Review which apps can reach your contacts and revoke any permission that is not needed. Do not forget to set up two-factor authentication on your accounts either. Not giving out a friend's number without asking, tidying your contacts regularly - everyday habits of this kind are what keep information that matters safe. Our article on what to watch out for when giving a friend your number is worth a look as well.