> We have built an extensive set of proprietary fuzzing tools for KVM. We also do a thorough code review looking specifically for security issues each time we adopt a new feature or version of KVM. As a result, we've found many vulnerabilities in KVM over the past three years. About half of our discoveries come from code review and about half come from our fuzzers.

Why aren't these tools being open sourced?

Some of the tools have been: https://github.com/google/syzkaller