Secret Debugger Found in AMD Chips

Wednesday Nov 17th 2010 by Keith Vance
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A secret debugger has been discovered on AMD Athlon processors that could allow for the chips to be reverse engineered.

A hacker who calls himself "Czernobyl" discovered a secret debugger installed on all AMD processors made in the past 10 years.

"AMD processors (Athlon XP and better) have included firmware-based debugging features that expand greatly over standard, architecturally defined capabilities of x86," Czernobyl said. "For some reason though, AMD has been tightly secretive about these features."

The debugger is password protected, but the hacker was able to brute-force it.

Tom Jowitt of eWeek Europe wrote, "There are concerns that the debugging feature could reveal exactly how AMD's chips work, allowing them to be reverse engineered. It also means that there could be a possible security risk, as Czernobyl published a full set of instructions for turning the debugging feature on."

Czernobyl brushed aside security concerns.

"What is described herein does not pose new security problems per se; after all MSRs and Control Registers aren't accessible except from ring zero," he said. "Nor are the Host's CRs and MSRs accessible from a properly designed Virtual machine. I doubt the newly disclosed features will open security risks that were not already present due to poor OS and/or virtualisation systems designs."


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