There's a new app that uses machine learning to mine your camera roll for explicit images. The purpose of the app, Nude, is to file these sensitive photos into a for-your-eyes-only folder, and then help you wipe the pics from your camera roll and iCloud. But algorithms are still not very good at picking up on the nuances of human behaviour -- and after letting Nude troll through my camera roll, I'm not convinced this algorithm has ever seen a naked body.