Apple has rolled out an update to its operating system this week with a feature called Stolen Device Protection. It makes it a lot harder for phone thieves to access key functions and settings, and users are being urged to turn it on immediately. The software update for iPhones and iPads addresses a vulnerability that thieves have discovered and exploited: allowing them to lock victims out of their Apple accounts, delete their photos and other files from their iCloud accounts and empty their bank accounts by accessing passwords kept in the Keychain password manager.