AB used to have a system that automatically suspended someone who posted lots of stuff in a very short time. (I know because I fell foul of it a few times when I split an answer across several posts -AB also had a very tight character limit on posts in those days).
However there's no longer any automated system. I'll sometimes flag up a 'possible spam' message on a thread from a first-time poster, who appears to be awaiting a link from another similar poster. (i.e. it's the 2-part spam trick). That's particularly likely if the post is is B&F, if it's written in 'Hinglish' or if the new member's username is made up of a forename and surname (possibly with a number on the end of it); they're all typical characteristics of spam here.
Other moderators are hopefully on the lookout for potential spam too but, obviously, a certain amount of discretion has to go into the decision-making.