Well, that’s what I would say if I had an iPhone 4S. According to Graham Cluley, a security analyst, Siri doesn’t require your iPhone 4S to be unlocked in order to access text messages, calendar or email. Cluley borrowed his co-workers brand-new phone, activated Siri, and composed both a text and email without ever unlocking the device. He also claims he could have messed with his appointments.
Don’t fret, this isn’t permanent. Under Settings> General>Passcode, you can disable Siri from the lockscreen. However, it seems illogical to allow in-depth access or no access. Perhaps there’s a good middle ground that hasn’t been considered yet, or even a spoken password. Cluley seemed disappointed that Apple chose the option that was “more about impressing your buddies than securing your calendar and email system.”
If you own a 4S, maybe you should disable Siri from the lockscreen, just to be safe.