One of the top posters on my super-full-locked server have posted over 900k items with his AHBot, and gained over 8million gold from AH (As It is listed under Statistics page on character Compare Achievments)
So I doubt there is any other way of detection, but massive reports.
Me personally started a "manual" war with an AHbot on a medium server, controlling the Glyphs market with 4 characters, relogging and reposting every 3-5min each, 18 hours per day. Even led him to verbally curse me, so I reported him, and he got ~48 or 72h suspension for verbal harrasment, but he continued to AHBot. So the GMs seems to not really care about accounts like that.