1 – Everyone with a WordPres site/blog has this same issue. Most of my sites see an averge of 30-50 SAM sign up attempts a day like this.

2 – It’s mostly an attempt for bots to post comment SPAM to get bd-quality backlinks for other sites out there. It’s a very common and well-known thing that the more black-hat SEO’s do. They just keep on sending the bots and SPAM because it really doesn’t cost anything for them to do it, so if one out of every 1,000 attempts gets a result, they make out pretty well with a few million attempts.

The thing to do is use one of the various anti-SPAM plugins out there. I’ve bene put onto Anitspam Bee by some of the people on the forum, and that has worked well fo me so far.