Austrian security researcher Peter Kleissner has posted a video showing the Stoned Lite bootkit successfully defeating Windows 8.
Here's the video:
Windows 8 Bootkit Demo from Peter Kleissner on Vimeo.
As you can see, the bootkit, which is only 14KB big, bypasses Windows UAC
and the security mechanism build into the Windows 8 bootloader.
Kleissner previously developed a proof-of-concept ‘bootkit’ called Stoned [PDF] capable of attacking Windows platforms ranging from XP to 7. It seems that this work has now been extended to include Windows 8. The source code to Stoned is available for download from Kleissner’s website.
According to Kleissner the new Windows 8 hack does not attack UEFI 'secure boot' feature and currently only works on systems running legacy BIOSes.