Is your USB drive at risk?

'Invisible yet fundamental' flaw that lets hackers take over computers discovered by security experts

Security researchers have long warned about the dangers of malicious files on infected USB sticks.

But now experts have discovered a much more dangerous threat that is even more widespread, virtually untraceable and much more difficult to solve than simply installing anti-virus software.

The Berlin-based researchers reverse-engineered the software files that control how the USB drive's software works - and revealed how this so-called firmware can be reprogrammed to take complete control of a PC.

Firmware is a software program, or set of instructions, programmed onto a hardware device.

It tells the device how to communicate with other devices, including computers.

Firmware can be thought of as 'semi-permanent' since it remains the same unless it is updated by a 'firmware updater'.

Firmware updates are installed the first time a device is used, for example, or to update a device so it works on a new operating system.

Drive manufacturers will often update firmware to improve the performance of their devices.

These changes are made at a central level before being pushed out to individual devices.

The flaw was discovered by Karsten Nohl and Jakob Lell at Security Research Labs has been dubbed BadUSB.

It affects thumb drives and external hard drives, but also any device that connects to a PC using USB.

This includes keyboards and the mouse, as well as the USB drives used to charge phones and tablets.

'The [USB] interface standard conquered the world over the past two decades thanks to its versatility.

' Almost any computer peripheral, from storage and input gadgets to healthcare devices, can connect over the ubiquitous technology. And many more device classes connect over USB to charge their batteries.

' This versatility is also