How does it get in?
The same way it all does, smarter bots. For every security measure we or anyone else employs to fight spam, the spammers come up with a counter measure. No one can stop it all. That is why we have Mods, to pick up the slack where the automated systems fall short.
All in all I think we are doing an outstanding job of keeping spam at bay. The hardest and most difficult type of spam to deal with? The human powered variety. Unfortunately the only solution for that kind of spam is the Admin powered ban hammer. It works well too. = )
+1 Core you guys do a GREAT job dude, keep it up. You have all the support we can give.