Since the early days of PCs, chips called DMA (Direct Memory Access) controllers were introduced to offload data intensive tasks from the processor. This technology is what made video game audio tolerable (through dedicated soundcards) and hard-drives "faster" (by not using Programmed IO) because the processor did not have to stop operations to devote cycles to these repetitive tasks. The elegance of a DMA attack is that a device with DMA hardware privileges can essentially read and write to any location in memory without processor intervention.

Without processor intervention – which means bypassing software security mechanisms – cracking into Windows computers just became a whole lot easier for hackers. If there is a IEEE1394 (commonly known as FireWire) port on the machine, gaining access is as simple as plugging in. The technique was first demonstrated (flash) three years ago against UNIX machines and was adapted in 2007 to work on Windows machines. FireWire’s OHCI interface protocol includes the ability for hardware devices to access RAM via DMA. Originally, debuggers used the technique to step through code in a test machine’s RAM. It did not take long for the unrestricted degree of access in the debugging tool to be transformed into a hacking vector to read/change passwords directly, copy swaths of data from RAM, alter the code for running applications or even extract secret encryption keys. It takes nothing more than a reprogrammed iPod, a FireWire cable and a few seconds to deftly compromise any machine left physically unattended.

UPDATE: Since the original demonstration, the technique has been refined for Linux to emulate the device and subsequently evolved into a capability working against more systems.