USB security flaw can expose user passwords

USB devices can be used to infect a computer without the user's knowledge, according to security researchers.

Karsten Nohl demonstrates how a significant flaw affecting the hardware can be exploited.

Using an otherwise normal smartphone, he shows the BBC's Dave Lee how a sophisticated attack can be carried out, while the user is completely oblivious.

The body responsible for the USB standard said manufacturers could build in extra security.