http://www.bbc.co.uk/news/technology-38012699
"A developer has created a $5 (£4) device that can hack into an unattended computer even with a locked screen.
The tool called Poison Tap can break into a password-protected computer if the user has left an internet browser running in the background.
The attacker can then remotely use the victim's web accounts undetected."
"... all users could do is make sure that they close their browser every time they leave their computer - even if it is locked.
A Microsoft spokesperson told the BBC: "Regardless of operating system, for this to work, physical access to a machine is required. So, the best defence is to avoid leaving laptops and computers unattended and to keep your software up to date".