Some ideas for anti-spam measures that might help:
block users who post flood -- e.g. if an account makes 10 posts a minute, it's a spammer
block accounts that end up massively in the negative shortly after they start posting -- e.g. an account at -50 within 15 minutes of making its first post is probably a spammer (exact thresholds may need some tuning). Note that this is different from blocking new accounts that go into the negative since people can register accounts in advance of an attack and wait until later to cause disruption.
block users who post repetitive comments/links excessively -- e.g. if the same link is in 10 comments/posts from the last hour or they've submitted the exact same comment a dozen times, the account is probably a spammer (again, thresholds may need tuning); that won't catch all the bots (one of them added a bunch of random words) but will catch some of them. More clever filtering could catch the other bots.
block new posters who are reported many times by established accounts in good standing -- at least until an admin can check what is going on