New Malware Can Bypass BIOS Security

May 25, 2013 – 8:24 AM

As more hardware vendors seek to implement the new NIST 800-155 specification that was designed to make the start-up BIOS firmware on our PCs and laptops more secure, they may need to rethink the security assumptions upon which the standard depends. A trio of researchers from The MITRE Corp. say that the current approach relies too heavily on access control mechanisms that can easily be bypassed.

The researchers are taking their message to Black Hat USA later this summer in a talk where they plan to unveil new malware proofs-of-concept that can trick an endpoint’s Trusted Platform Module (TPM) chip into thinking the BIOS firmware is clean and can persist infecting the BIOS after it has been flashed, or reset, or even after it has been updated.

“The NIST document is sort of emphasizing access control mechanisms as a way to protect firmware,” says Corey Kallenberg, security researcher with MITRE. “Whereas our stance is, look, access control mechanisms are going to fail, you have to assume that the attacker is going to find a way to get into your firmware.”

His colleague, John Butterworth, says there already has been an established history of researchers who have managed to bypass access controls in the BIOS.

“For example, Invisible Things Lab showed in 2009 how firmware signing could be bypassed to arbitrarily modify the BIOS,” he says. “We believe that this trend will continue in the future.

Together with Xeno Kovah, lead infosec engineer at MITRE, Butterworth and Kallenberg are taking these bypass methods a step further with the research they’ll unveil at Black Hat, which support their claims about the insecurity of the current methods used to assure the integrity of the BIOS.

Currently, system TPM chips depend on code stored on the BIOS flash chip to perform a BIOS measurement and send that platform configuration register (PCR) value to the TPM chip as an assurance that the BIOS remains unmolested. In most cases, if the BIOS is manipulated, then the PCR value will change and will break the chain of trust with the TPM.


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