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Assume you give your iPhone (iOS 12.2) + passcode to someone (e.g. teacher, law enforcement, airport security, etc.) for several hours, and then they give you your iPhone back.

Assume the person is technically skilled and motivated to harm your data or compromise your security/privacy after the device is handed back.

What harmful things can they do to your data/privacy/security? What traces would be around to identify those actions?

In particular, I'm interested in harmful discrete things (e.g. setting up a proxy so all web traffic is monitored). The non-harmful and easily detectable things (e.g. changing your iPhone's background) could be good to document as well, though.

  • I’m going to edit this so the question is clear and all the portions of the answer can be added to the best answer. – bmike May 22 at 18:05
  • I hope the answer is sought keeping ethical intent in mind, and you are not seeking to misuse it. – Nimesh Neema May 22 at 18:42
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    That thought never crossed my mind, but thanks for calling that out @NimeshNeema! Basically once my phone is handed back to me, I'm wondering what should I check to ensure that my security/privacy wasn't compromised – Senseful May 22 at 18:44
  • @NimeshNeema I don't think you need to worry too much about unethical people using these means, because that's essentially the security/privacy by obscurity argument. The bad attackers will find means to compromise someone's privacy/security and they won't share it. One of the best ways to fight it is to put it out there so everyone knows about it and can protect themselves against it. – Senseful May 22 at 18:47
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    All tools and knowledge can damage or be put to evil use. We have to take the stand that documenting how things work and truthful, detailed technical data will help people be educated and safe knowing the facts. – bmike May 22 at 20:24
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I hope the information in the answer is used keeping ethical intent in mind, and there's no intention to misuse the information.

What harmful things can they do?

Playing devil here, I would do the following:

  1. Change fingerprint/face data for use with Touch ID/Face ID. I'd remove existing fingerprints/faces and add mine. (This action could go somewhat undetected in case wherein you have multiple fingers registered. I could remove just one finger and register one of mine. This would however be caught when accessing 1st party app such as App Store, where you are asked for your Apple ID password, as discussed in point #3 below).

  2. Change the passcode itself. (This could go undetected initially, until you chance upon entering the passcode, say for example after a restart).

  3. If I change the Touch ID/Face ID data, I'll obviously be able to lock and unlock the iPhone freely without restrictions using either Touch ID/Face ID or Passcode.

    Having entered my own Touch ID/Face ID data will give me access to host of settings. I'd also be granted access to the whole host of 3rd party apps that were protected by Touch ID/Face ID, such as WhatsApp, Dropbox etc. (Although 1st party apps such as App Store will require you to enter your Apple ID password before enabling new fingerprint/face data). Some 3rd-party apps such as 1Password are well guarded as they will ask to authenticate via the account password before enabling newly registered fingerprint/face data.

  4. I'd be able to send unintended messages using commonly used chat apps such as Messages/WhatsApp to contacts. I'd also delete the conversation to remove the traces.

  5. Wipe data off iCloud. This will lead to irreversibly losing critical data synced to and stored on iCloud such as contacts, emails, photos, notes, documents etc.

  6. Remove data stored and synced on iCloud by 3rd-party apps.

  7. Uninstall apps freely which will likely cause you to lose locally stored/non-backed up data.

  8. Remove other devices linked to your Apple ID via iCloud settings.

  9. Change privacy settings by enabling/disabling specific apps access to location/contact data etc.

  10. Simply access/copy-off private data such as contacts, notes, photos without changing anything as discussed above and thus, you never noticing it.

  11. Copy data off your iPhone from apps that support File Sharing. Once simply needs to unlock iPhone, connect to a computer with iTunes installed and trust both on computer and the iPhone.

  12. I'd be able to link a brand new device to your Apple ID using iOS Quick Start. If your email client app if set up on the iPhone with your Apple ID email, I'd delete the email alert that you receive when a new device is linked to your Apple ID.

  13. Delete the call log from Phone app.

  14. Leave app reviews and ratings on the App Store. This may be hard to notice easily.

  15. Enable/tweak Family Sharing and invite myself your family. I can then access paid apps and music on my device. After doing the deed, I can also remove myself from Family Sharing or disable it, and remove the traces.

I would obviously not be able to access/change settings which require Apple ID password. This includes turning off Find My iPhone and logging out/resetting the iPhone.


What trace would be around to identify those actions?

From the user standpoint, there could be minimum to no traces to identify the actions. There's no on device mechanism to access device access logs.

Assume that the user never attempt to unlock the iPhone or apps using Touch ID/Face ID and always use the Passcode. They could still access and copy off data such as photos, contacts via unidentifiable medium such as AirDrop.


It appears that Face ID is slightly better at protecting you here compared to Touch ID, as it currently allows only one face to be registered at a time.

  • Regarding I'd be able to send unintended iMessages to contacts, I would append , and delete them so you have no trace on your phone they were sent. The attacker is not only going to be malicious, but also stealthy – Senseful May 22 at 18:42
  • Is adding a new trusted device to iCloud possible? Cause that could be a huge security risk as well – Senseful May 22 at 18:51
  • @Senseful Sadly yes. I'd be able to use Quick Setup to link a new device to the Apple ID, without needing Apple ID password. – Nimesh Neema May 22 at 18:58
  • You can reset the Apple ID password with the device password support.apple.com/en-us/HT201487 – Ezekiel Elin May 22 at 22:53
  • They can add a trusted phone number to the account as well. This is visible in Settings > [your name] > Password & Security > Trusted Phone Number. – Senseful Jun 11 at 19:55
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They could change your password on any website that has a password reset mechanism based on either:

  • sending a password reset email to an email account set up on your device, or
  • two-factor authentication using your device.

They could order goods or services or make payments if you have apps that allow this.

With access to your email and any other sources of information on the device such as online banking apps, there is a chance they could use a 'privilege escalation' approach to gain more access to accounts or services, by collecting enough information to be able to answer the security questions needed to give instructions or make changes over the phone. For example your home address is probably in your Contacts, some apps store your date of birth, an online banking app might show details of recent transactions, and that might be enough to allow them to change your registered postal address which they could then use to request new credit cards or card PINs, reset online banking passwords if the bank only allows this by post, and so on.

They could delete any email records of these actions, but probably not the online records of orders or bank transactions.

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