Slashdot Mirror
VM-Based Rootkits Proved Easily Detectable
paleshadows writes "A year and a half has passed since SubVirt, the first VMM (virtual machine monitor) based rootkit, was introduced (PDF), covered in the tech press, and discussed here. Later Joanna Rutkowska made news by claiming she had a VMM-based attack on Vista that was undetectable — a claim that was roundly challenged. Now in this year's HotOS workshop, researchers from Stanford, CMU, VMware, and XenSource have published a paper titled Compatibility Is Not Transparency: VMM Detection Myths and Realities (PDF) showing that VMM-based rootkits are actually easily detectable."
I'm still convinced that it's possible to make a VM that appaears to software running within as real hardware.
The paper, however, takes a practical approach, examining how some industry standard VM-s operate, such as VMWare and Virtual PC.
Those VM-s take plenty of shortcuts to improve performance, and don't virtualize some instructions, rather remap them, or "shift rings" of execution etc. as much as possible so to take advantage of the hardware while remaining sandboxed. They don't virtualize the clock as well, so you could time the performance.
A rootkit isn't competing with other rootkits based on performance, it does so based on how undetectable it is. It's arguably a different problem. I think we're yet to witness what a full blown VM made to be a rootkit will act like, and whether it'll be detectable.
Unfortunately, this paper completely misses the point. This paper is not so much about detecting a VM based rootkit so much as it is about detecting VMs in general. The authors argue is that if you detect a VM when you aren't expecting to, you've found a rootkit. Joanna's argument is that in a few years, everything is going to be using VM technology and you won't be able to tell a "good" VM from a "bad" one.
See virtualization-detection-vs-blue-pill and her presentation on the subject here. No one ever said that detecting a virtual machine is impossible. They are saying discriminating between malicious and non-malicious VMs is impossible.
VMWare is virtualization software, not emulation software. It runs pretty close to native speed, depending on what you run on it. Comparing it to bochs is just stupid, that's a full blown emulator. A VM still uses your processor natively to decode the majority of instructions, it just catches the privileged ones, that otherwise would make your OS go boom. (Simply put)