We hate to break it to you, but your PC is not as secure as you think. That remains true even if you lock your computer with a password. Should you leave your system unattended, it would be possible for someone to hack into it in less than a minute using a $5 Raspberry Pi device. The culprit doesn’t even need advanced knowledge of computer

Source: Hot Hardware – PoisonTap Device Can Hijack Your Locked Computer In 1 Minute Over USB