By default, anyone can use Siri to send e-mails or text messages from a locked phone without having to enter a passcode. The default setting should prevent any use of Siri while the phone is locked. For Siri to be both secure and useful when locked, we need new ways to access the phone. In the meantime, I hope Apple changes the iPhone 4S’s default settings to keep Siri locked behind a password-protected screen. The face recognition in Android Ice Cream Sandwich is a good idea, as is the thumbprint reader on Motorola’s Atrix.”]
Source: https://www.csoonline.com/article/2129887/siri-s-security-hole–the-passcode-is-the-problem.html