They are aggressive to unknown people, while not being aggressive to the owner and people the dog is familiar with, if left alone with unknown people it will flip out.
Witnessing this directly, the owner of said dog had absolute complete control while in its presence, it would do whatever it was told, when said owner went to the toilet, the dog seemed extremely aggressive and wouldn't follow orders.
Luckily I was able to release a moment of pure evil, so the dog **** itself, and ran under the sofa, however if it was someone other than myself, no doubt some sort of violence would have taken place... However since that day the dog wasn't itself, suffered from depression and eventually ran in front of a car.
Generally, all breeds which possesses enough strength to do any serious damage should not be allowed as pets without a specific license with specific requirements I.e. people in sparse rural areas, or organised dog fighting events.