I blogged MuSecurity 6 weeks ago. Today's announcement of a $10 million investment comes as no surprise. Mu has technology that attacks protocols. Any device, especially a security device on your network has the potential (of about 99.9%) of having vulnerabilities in the way it interprets protocols. The problem is the huge amount of interlaced and occasionally conflicting RFC's that define these protocols. A determined hacker (or security researcher) usually uses manual techniques to find a vulnerability. He will throw malformed packets at the device until he can get it to choke, roll over or die.
MuSecurity automates this process by generating attacks via permutation. I would think Mu's primary customer would be security appliance vendors but I understand they are going directly after the large enterprise. I can see how a lab would use their tool to compare and verify the security posture of competitive products.
Nice to see innovation in the security space. Also nice to see investors that get it.