Brazilian black hat community
I am a manager of an ISP in a Portuguese speaking country that has the misfortune to have the same name as a Brazilian location.
So, up to the point: it is unbelievable the amount of crap that comes from brazil IP addresses. Loads of spam, and fake e-mails with custom-made trojans are the order of the day. And even tough most of them are blocked by our measures, some manage to pass. yahoo.com.br also seems not to care much about our spam complaints, unfortunately.
In my opinion, in terms of this activity, Brazil comes right next after china and russia. Or perhaps due to our peculiar case, even manages to surpass russia.