Frat houses[1] are known for having a lot of parties. This partying will crescendo around the university's graduation date. DEFCON is being compared to one of these peak parties.

Black Hat is a bit more subdued. It costs a lot more to attend Black Hat. Black Hat parties are more like casual social gatherings. I believe that in Europe, country clubs are more likely to be called gentlemen's clubs. In either case, it's usually the richer people attending.

[1] https://en.wikipedia.org/wiki/North_American_fraternity_and_...