2 Control Your Lock Screen
For the particularly privacy conscious, an iPhone’s Lock screen can represent a security hole. By default, there are several features that are accessible even when your device is locked — including Siri, the Notifications View, and the ability to reply to iMessages.
Thankfully, you can disable most of these features from the Lock screen in the Settings app. Just go to General > Touch ID & Passcode, and toggle the features that you want to restrict when your iPhone is locked. Disabling Siri is a good idea, as is turning off Reply with Message.