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Researcher creates proof-of-concept malware that infects BIOS, network cards

New Rakshasa hardware backdoor is persistent and hard to detect, researcher says

By Lucian Constantin, IDG News Service
July 29, 2012 04:05 PM ET

IDG News Service - Security researcher Jonathan Brossard created a proof-of-concept hardware backdoor called Rakshasa that replaces a computer's BIOS (Basic Input Output System) and can compromise the operating system at boot time without leaving traces on the hard drive.

Brossard, who is CEO and security research engineer at French security company Toucan System, demonstrated how the malware works at the Defcon hacker conference on Saturday, after also presenting it at the Black Hat security conference on Thursday.

ANALYSIS: The future of malware

Rakshasa, named after a demon from the Hindu mythology, is not the first malware to target the BIOS -- the low-level motherboard firmware that initializes other hardware components. However, it differentiates itself from similar threats by using new tricks to achieve persistency and evade detection.

Rakshasa replaces the motherboard BIOS, but can also infect the PCI firmware of other peripheral devices like network cards or CD-ROMs, in order to achieve a high degree of redundancy.

Rakshasa was built with open source software. It replaces the vendor-supplied BIOS with a combination of Coreboot and SeaBIOS, alternatives that work on a variety of motherboards from different manufacturers, and also writes an open source network boot firmware called iPXE to the computer's network card.

All of these components have been modified so they don't display anything that could give their presence away during the booting process. Coreboot even supports custom splashscreens that can mimic the ones of the replaced BIOSes.

Existent computer architecture gives every peripheral device equal access to RAM (random access memory), Brossard said. "The CD-ROM drive can very well control the network card."

This means that even if someone were to restore the original BIOS, rogue firmware located on the network card or the CD-ROM could be used to reflash the rogue one, Brossard said.

The only way to get rid of the malware is to shut down the computer and manually reflash every peripheral, a method that is impractical for most users because it requires specialized equipment and advanced knowledge.

Brossard created Rakshasa to prove that hardware backdooring is practical and can be done somewhere in the supply chain, before a computer is delivered to the end user. He pointed out that most computers, including Macs, come from China.

However, if an attacker would gain system privileges on a computer through a different malware infection or an exploit, they could also theoretically flash the BIOS in order to deploy Rakshasa.

The remote attack method wouldn't work in all cases, because some PCI devices have a physical switch that needs to be moved in order to flash a new firmware and some BIOSes have digital signatures, Brossard said.

However, Coreboot has the ability to load a PCI extension firmware that takes precedence before the one written on the network card, therefore bypassing the physical switch problem.

The attack "totally works when you have physical access, but remotely it only works 99 percent of the time," Brossard said.

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