We are working with Stack Exchange to attempt to figure out how to automatically block these types of spam edits. Initially we asked them to block anonymous edits on our community but it turns out this is not something they can easily do.
For now, the best thing you (and everyone else) can do is to reject these edits when they come up for review.
We continue to have problems with anonymous spam edits to the accepted answer to Should I install the Content Delivery web sites and services with Integrated Application pools?
Stack Exchange has rolled out some changes to their spam detection/blocking algorithms which now identify those edits as likely spam edits but they still go into the queue for community review. As we continue to get 2 or 3 of the edits on that one question per day I have permanently locked the answer.
Later on, if the spam situation is resolved a moderator can unlock the post but for now this should block most of the spam edits we are receiving. I would not however that we have at least one other answer on another question which has also received a few anonymous spam edits so it could be the spammers will just change their target to that answer.