In a technical analysis of the UK NHSx contact tracing app for iOS, security engineers find that Apple's Bluetooth design makes it harder to detect iPhones running the app in background mode, and the app is using "keepalive" notifications in order to keep the app able to make the necessary connections. The researchers believe this workaround will work sufficiently well for users in populated areas. The app appears to abide by the privacy safeguards listed in the paper released by the National…