Grey hats are a mixture of both a black hat and white hat (obviously). They hack like white hats, but instead of telling a company their security holes privately, they expose these weaknesses publically, allowing the company a very slim to no chance of fixing these flaws before a black hat can take advantage of these flaws. They usually alternate between being a black and a white hat.
Adrian Lamo is another hacker that found himself in trouble after the F.B.I was able to probe his illegal actions. He never stayed at one location to perform his hacking. He is well known for exploiting companies such as Microsoft, the New York Times, Lexis-Nexis, and Yahoo!.
Cohen was able to create the first computer virus. The virus he created was able to completely overtake a computer and control each one of its functions.Cohen was also able to create good viruses. As silly as it sounds, he was able to create a virus that did nothing malicious to a computer. After putting the virus on a computer, it went into each executable file (.exe) and made them smaller.