"Hacker Finds Hidden 'God Mode' on Old x86 CPUs"
Some x86 CPUs have hidden backdoors that let you seize root by sending a command to an undocumented RISC core that manages the main CPU, security researcher Christopher Domas told the Black Hat conference here Thursday (Aug. 9)
The backdoor completely breaks the protection-ring model of operating-system security, in which the OS kernel runs in ring 0, device drivers run in rings 1 and 2, and user applications and interfaces ("userland") run in ring 3, furthest from the kernel and with the least privileges. To put it simply, Domas' God Mode takes you from the outermost to the innermost ring in four bytes.
"We have direct ring 3 to ring 0 hardware privilege escalation," Domas said. "This has never been done."
So, how many other backdoors exist in current computers and other electronic devices? That's why, as with software, hardware should be open source, free as in freedom. Although you can't patch hardware as easily as you can patch software, that's for sure.