Unapproved Comment Spam

I recently got a message from Dreamhost saying they had to deactivate my website because of comment spam and the load it was putting on our servers.

I knew it was coming in awhile ago, so I deleted all the comments, removed the ability to comment, and switch to a comment system that required a facebook login to use.

Well, apparently spambots can still send comments to your posts, and it puts pressure on your server even if they are marked unapproved.

What more do I need to do to stop this from happening? Even when I have no “comment field” on my sites, they still manage to get comments into my dashboard and I have to approve or unapprove.

What’s the best solution to this?

Thanks!