Have you heard about "default allow" and "default deny" in the domain of cyber security? Traditionally PCs, especially for home use, were built around the former idea, where the user supposedly trusts most of the stuff installed.

The problem is that malware may sneak in, and then the user needs a horrible piece of software called anti-virus that needs to apply complicated heuristics to try and separate one from the other. It kind of worked ok for many years, but as the world evolved and the dangers kept increasing, little by little we have been going towards the other idea – default deny – where apps are considered harmful until proved otherwise, and the honest app developers have to jump through multiple hoops to get their apps available to users. That's the app store model, which kind of works, but is cumbersome and expensive for the app developer.

Anyway, going back to the VM discussion, I think we may end up applying the default deny idea further into the OS Kernel to reduce those risks further. After all, a small kernel has a much smaller risk surface and perhaps it can be formally verified to be secure under some reasonable assumptions.