The 72-hour event is not an automatic passcode change or permanent lockout. Magnet Forensics describes iPhones that reboot after remaining locked and unused for 72 hours. That reboot moves the device from After First Unlock (AFU) to Before First Unlock (BFU), making more data unavailable until the passcode is entered. A leaked law-enforcement training video separately claims that Magnet’s GrayKey Preserve and its Evidence Preservation Mode can retain an AFU state through a reboot, but independent testing has not established how well that claim works on current iPhones.
What the 72-hour behavior actually is
When an iPhone has stayed locked without being unlocked for 72 hours, iOS can reboot it. The security consequence is more important than the restart itself: after boot, the phone is in the BFU state and requires its passcode before the broader set of protected data becomes available.
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- The phone is seized, powered on and already unlocked at least once since its previous boot.
- It remains locked and is not unlocked for 72 hours (three days).
- iOS reboots the device.
- The reboot changes its forensic state from AFU to BFU.
- Entering the passcode is required to return to the more accessible AFU condition.
This is why a seized phone can become harder to examine simply by sitting untouched. The timing is described in Magnet Forensics documentation and in 2024–2026 reporting; it is not a claim that every iPhone becomes unusable after three days.
AFU and BFU: the security distinction
| State | How the state is reached | Practical forensic significance |
|---|---|---|
| After First Unlock (AFU) | The phone has been unlocked since its last reboot. | More data is available to authorized forensic tools than in BFU. |
| Before First Unlock (BFU) | The phone has rebooted and its passcode has not yet been entered. | More encryption-protected data remains unavailable until the passcode is supplied. |
The 72-hour inactivity reboot therefore narrows the window in which investigators can try to preserve an AFU device after a seizure. AFU does not mean a phone is unencrypted, and BFU does not mean every piece of data is inaccessible; the terms describe the different key and data-access conditions after boot.
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What GrayKey Preserve is reported to do
404 Media reported on a leaked Magnet Forensics training video describing a product called GrayKey Preserve and an Evidence Preservation Mode for existing GrayKey hardware. The stated purpose is to capture or preserve the phone’s AFU condition so that an inactivity reboot, loss of power or another reboot does not remove that condition.
“That AFU state is captured,” the Magnet employee says in wording reproduced by 9to5Mac. “Even if that device does reboot for any number of reasons, memory maintenance or the power is lost or whatever, the AFU state is not lost. This is the true magic behind the GrayKey Preserve and the Evidence Preservation Mode function.”
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In plain terms, the claim is about preserving an already obtained forensic state. It is not a public announcement that GrayKey can derive an iPhone passcode, turn a BFU phone back into AFU, or defeat Apple’s passcode protections on demand.
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| Question | What the available reporting supports | What remains unconfirmed |
|---|---|---|
| Does the 72-hour reboot exist? | Magnet documentation and independent reports describe a reboot after 72 hours locked and unused. | The evidence cited here does not provide a model-by-model prevalence rate. |
| Is AFU/BFU the relevant distinction? | Yes. The reboot moves a device from AFU to BFU, reducing access to protected data until passcode entry. | The exact data set available on any particular model or iOS build is not stated. |
| Does GrayKey Preserve retain AFU after reboot? | A leaked Magnet training video names GrayKey Preserve and Evidence Preservation Mode and makes that claim. | The technical mechanism, supported iPhone models, supported iOS releases, availability date and real-investigation success have not been independently verified. |
| Has Apple endorsed the feature? | No Apple endorsement is reported. | Apple and Magnet did not respond to the comment requests cited by 9to5Mac, which said the technology’s current effectiveness was unclear. |
That distinction matters because a vendor training statement is evidence that the feature was presented, not reproducible proof that it works on every current device. No public independent success-rate test is established in the cited coverage.
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Do not confuse this with Apple’s other 72-hour feature
Apple uses the same 72-hour number for a different consumer feature in iOS 17 and later. After a user changes a passcode, iOS allows the previous passcode for 72 hours so the user can recover access if the new one is forgotten. That grace period does not cause the forensic inactivity reboot.
| Feature | Trigger | Result | Who it serves |
|---|---|---|---|
| Inactivity reboot | Phone remains locked and not unlocked for 72 hours. | Reboot; AFU becomes BFU until the passcode is entered. | iOS security and lawful forensic handling. |
| Previous-passcode recovery | User changes the passcode in iOS 17 or later. | Previous passcode can be used for up to 72 hours to regain access. | The device owner. |
Apple also documents increasing delays after failed passcode attempts and protections around keychain and other data. None of those documents, as cited in the coverage, endorse GrayKey Preserve.
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What this means for investigators and iPhone owners
For lawful investigators
The reported workflow is about evidence preservation immediately after a device is lawfully obtained. Keeping a phone powered and untouched may not be enough if the 72-hour timer is running; a reboot can change the cryptographic state before examination. Any agency would need to confirm with Magnet which GrayKey Preserve or Evidence Preservation Mode combinations, iPhone models and iOS builds are currently supported, and validate the result under its own legal and evidentiary procedures.
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For ordinary iPhone users
There is no indication in the cited material that GrayKey Preserve is a consumer product or a way for an owner to bypass a forgotten passcode. The practical protection remains the passcode itself, prompt installation of security updates, and careful handling of a device that has rebooted: after a restart, the passcode is required before normal biometric unlocking can resume.
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The bottom line on the reported workaround
iOS’s 72-hour behavior is a security reboot that moves a phone from AFU to BFU, not a secret three-day passcode expiration. GrayKey Preserve may be designed to preserve AFU through that reboot, according to a leaked Magnet training video, but its mechanism, current compatibility and effectiveness remain unverified in independent public testing. Treat it as a law-enforcement forensic capability claim—not a demonstrated universal bypass of iPhone security.
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