Last week, I heard lots of talk about "hyperjacking," which was described as a new threat that we'll be facing soon. Hyperjacking is a hypothetical attack that goes after a computer that's running one or more virtual machines, like you might get in a cloud computing environment. The idea is that an attacker would target the operating system that's below the VMs, so that his attack program can run and the applications on the VMs above it will be totally oblivious to its presence.
I don't think that anyone's actually demonstrated hyperjacking yet, but it certainly sounds like an interesting idea. Maybe the move towards cloud computing will encourage hackers to move the idea from just idea to actual implementations. We'll probably hear more about this in the future.