This is a high-level question that may appear "obvious", but it's not, otherwise it would be addressed in the FAQ.
I believe the answer is, "community members take care of spam and spammers after they appear, manually, and there is no pro-active filtering performed by the software to block fresh spam and new spammers"
...but I'm not positive.
Sadly, not everyone can use Stack Exchange for their communities, but everyone can learn from Stack Exchange, hence my question.
I want to know how spam is dealt with, and how effective the methods are.