Android 15 may be able to quarantine misbehaving apps

The Android operating system offers robust protection against malicious and misbehaving apps. Even so, bad apps will sometimes slip through the cracks, in which case Google Play Protect might step in and automatically remove them. Like any advanced anti-malware software, Play Protect won’t be 100% accurate in its detections, which is why it usually errs on the side of caution and asks the user if they want to remove a potentially harmful app. With the upcoming Android 15 update, the system may add a new way for services like Play Protect to protect users from misbehaving apps: by quarantining them.

If you’ve ever dealt with anti-virus software on desktop operating systems like Windows, then you may be familiar with the concept of quarantining software. When anti-virus software quarantines a file, it’s because it suspects it’s malicious but is either unable to delete it or leaves the decision to the user because it’s unsure if the file is actually malicious. Quarantined files are isolated from the rest of the system so they can’t be executed, ensuring that whatever malicious software is potentially in them can’t do any dirty work.

The traditional concept of quarantining software doesn’t really exist in Android, mostly because the operating system was designed from the ground up to be safe from viruses. Apps can’t get system-level access, are sandboxed by default, and can only communicate with one another using well-defined APIs that they can only access if they’re granted well-defined permissions. That’s why you don’t really need to download a third-party antivirus or anti-malware app for Android. Since Android doesn’t work the same way as Windows, it’s no surprise that quarantining software on Android will work a bit differently than it does on Windows.

Android 15 app quarantining: How it might work

When an app is quarantined in Android, it will behave differently than a non-quarantined app. It will still be visible in the user’s home screen launcher and in Android Settings, but a few restrictions will apply to it:

1. Notifications from it won’t be shown
2. All its windows will be hidden, and already-started activities will be stopped
3. It won’t be able to ring the device
4. Its services can’t be queried by other apps (though its activities can)
5. It can’t be bound to or receive broadcasts from the system or other apps
6. It can’t be resolved (i.e., it won’t show up in the intent disambiguation dialog)

Quarantined apps thus act similarly to disabled apps, though disabled apps don’t appear in the home screen launcher. Quarantining an app is also similar to suspending it, an action taken by the Digital Wellbeing service to pause distracting apps, except individual components of quarantined apps can behave as disabled, as previously mentioned. Thus, it’s safe to say that the new quarantined state lies somewhere in between the existing suspended and disabled states.

In fact, the APIs used to quarantine an app are the same ones used to suspend an app, except an extra flag is passed. During testing and development of this feature, system apps with the SUSPEND_APPS permission were allowed to quarantine apps, but the methods in question have since been updated to require the use of the new QUARANTINE_APPS permission. This permission can only be held by the system “verifier” app or by an app signed with the same certificate used to sign the OS. So only services like Play Protect, which is part of the Google Play Store, will be able to quarantine apps.

Unfortunately, I don’t know when Google will actually launch this new feature. I first spotted evidence of app quarantining back in Android 14 QPR2 Beta 1 in November, but the developer page for “Quarantined Apps” has since been removed. The feature flag enabling OS-level support for app quarantining is still present, but there’s no way to quarantine apps manually, even through the command line. Plus, neither the Google Play Store nor Google Play Services apps currently request the QUARANTINE_APPS permission. Thus, it’s entirely possible this feature won’t launch in Android 15 but might instead end up in a future release.

When app quarantining does launch, the UI shown above will likely be tweaked a bit. Apps calling the API to suspend or quarantine an app can customize the dialog that’s shown to the user when they attempt to launch a suspended or quarantined app. Whatever system app ends up implementing Android’s app quarantining feature will likely customize the dialog to say something like, “[X] app has been quarantined for your safety” followed by an explanation for why it’s been quarantined.

Although Android hasn’t needed an app quarantine feature for a long time, I’m still glad to see it added because it’s impossible for services like Play Protect to be 100% accurate, even if that system does a really good job at catching malicious and misbehaving apps.