Apple appears to have removed Private Photos (Calculator%) from the App Store.
Apple appears to have removed from the App Store a controversial app used by teenagers to hide photos behind a fully functioning calculator.
Private Photos (Calculator%) first gained attention in 2015 when US district attorney Pamela Casey's warning to parents about the app's true purpose went viral on Facebook.
It has since appeared on danger lists for parents drawn up by digital safeguarding experts, and last week, a British police unit confirmed that the app formed part of an undisclosed investigation.
Now, just days after Durham Police urged parents to be "vigilant" about Calculator%, the app has vanished from Apple.
It is no longer available on the App Store and a link to the app on developer Digital Mind Co's website is dead. A cached version of Digital Mind Co's store on Apple shows that the app was available to download as recently as last month.
Apple did not respond to Business Insider's repeated requests for comment. Digital Mind Co did not immediately respond to a request for comment.
The Calculator% app is marketed on the App Store with pictures of women in bikinis, hardly disguising its purpose to hide photos that are perhaps intimate in nature.
Users download the app and its icon looks like an innocuous calculator. Once open, users can input a secret code into the calculator and it opens a secret vault of images and video concealed to anyone without access.
Digital Mind Co has developed similar apps, including one that acts as a private browser. But like Calculator%, they no longer appear to be on the App Store. Digital Mind Co's calculator apps are not available on Android either.
Apple appears to have removed imitations as well, such as Calculator App Lock and Piano Pass, which asks users to play a secret tune to unlock their images. Some imitations are still on Android, however, including Calculator+ and Calculator Vault.
Durham Police would not disclose any details about its investigation, but a spokeswoman told Business Insider: "The Calculator app is essentially a secret photo album that children can use to hide photos or videos from their parents. The photos are hidden from view behind an icon that looks like a calculator. We would urge parents to be vigilant and discourage their children from using such an app."