BlueHat (or Blue Hat or Blue-Hat) is a term used to refer to outside computer security consulting firms that are employed to bug test a system prior to its launch, looking for exploits so they can be closed. In particular, Microsoft uses the term to refer to the computer security professionals they invited to find the vulnerability of their products such as Windows.
Blue Hat Microsoft Hacker Conference
An event that is intended to open communication between Microsoft engineers and hackers is called Blue Hat Microsoft Hacker Conference. The event has led to both mutual understanding as well as the occasional confrontation. Microsoft developers were visibly uncomfortable when Metasploit was demonstrated.
References
BlueHat Wikipedia(Text) CC BY-SA