# Push-Notifications

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>
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## Deleted messages can be recovered through push notification cache

Push notifications are those nice little messages on your lock screen, that show you
previews of the messages you received.

> [!warning] Warning {static}
>
> In early 2026 it became public that the
> [FBI could recover signal messages](https://web.archive.org/web/20260409150356/https://www.404media.co/fbi-extracts-suspects-deleted-signal-messages-saved-in-iphone-notification-database-2/)
> on an activists iPhone through iOS's own push notifications, although the > activist
> had self-destructing messages enabled and deleted their entire Signal app before the
> [confiscation](https://wiki.aktivismus.org/books/it-sicherheit-esc-it/page/confiscation).

The problem is that the operating system "caches" the content of the push notification
on it's own storage, meaning it stores your messages outside of the app itself. Thus,
deleting messages inside of the messenger itself won't delete the copies in the
operating systems cache.

> [!technical] What is caching?
>
> Caching is a technique used in computing to store copies of data temporarily, allowing
> for faster access to that data in the future. It helps improve performance by reducing
> the time it takes to retrieve frequently accessed information.

This is also true for self-deleting messages e.g. on
[Signal](https://wiki.aktivismus.org/instructions/signal.md#self-destructing-messages), which we recommend as a
security feature.

> [!tip] Tip {static}
>
> The only way to prevent the operating system from caching your messages, is to stop
> the app from displaying sensitive content in those push notifications.

Preventing caching can be done per app, as far as the single app provides such settings.
See our instructions for
[disabling sensitive content in signal notifications in Signal](https://wiki.aktivismus.org/instructions/signal.md#restrict-push-notifications).

## Information leak through notifications on lock screen

It is also recommended to completely disallow sensitive content showing up on your lock
screen for all apps on the operating systems level in you phones settings.

> [!tip] See
> [our recommendation](https://wiki.aktivismus.org/recommendations/graphene-os.md#more-security-and-privacy) on
> that for GrapheneOS.