The phones the FBI sold to crooks for a sting operation weren't just running a custom app — it appears the operating system was also tweaked for those goals. Motherboard has obtained one of the "Anom" phones (really, a modified Pixel 4a), and its mysterious "ArcaneOS" has a number of customizations that you wouldn't necessarily expect, even for a privacy-oriented phone.
For one, there are no app stores. You also can't toggle location tracking. And don't think you can simply flash the device with third-party firmware to make it behave more like normal phones — the bootloader is locked even though the startup screen tells you the device has been modified.
Some user said Anom was based on the existing GrapheneOS, but Anom may have lied to buyers about the software to instill a false sense of trust.
The interface does include some security features that would appeal to the criminal target audience, including a hidden chat app (accessed through the "calculator" when it worked) and PIN scrambling. A wipe code feature that lets you erase a phone from the lock screen is also present, although the Justice Department clearly didn't like that feature when it charged some Anom developers with alleged obstruction of law enforcement.
At least one second-hand Anom phone owner say they got a Pixel 3a, suggesting the FBI transitioned to different devices as the sting unfolded.
You wouldn't want to buy one of these devices, then, even for curiosity's sake. However, it's now clear just how far the FBI went to bust criminals. The agency wanted to give unsuspecting drug dealers the impression they were using a true encrypted phone, right down to the OS, even as the device quietly exposed messages to law enforcement agents.