Want to break into the computer network in an ultra-secure building? Ship a hacked iPhone there to a nonexistent employee and hope the device sits in the mailroom, scanning for nearby wireless connections.

How about stealing someone’s computer passwords? Forget trying to fool the person into downloading a malicious program that logs keystrokes. A tiny microphone hidden near the keyboard could do the same thing, since each keystroke emits slightly different sounds that can be used to reconstruct the words the target is typing.

Hackers at the DefCon conference here were demonstrating these and other novel techniques for infiltrating facilities Friday.