Vulnerability Research Companies?

What vulnerability research companies are out there? I just started working for one that is a government contractor and they do real work. It was hard to believe that the government really comes to these and other people with a device or a set of devices and asks them nicely to break into them in a repeatable fashion, i really thought it was all done in house. What other companies exist in this sphere? Are they all pretty small shops? …

companies cybersecurity research vulnerability vulnerability research