I downloaded and installed the latest version of SMF twice and before making any entries or making it available to the public hundreds of 'guest users' and thousands of posts appeared in the Forum Stats. The URL is www.TheConservativePoll.com/Forum .
well, your site registration is OPEN and you have no "protection" except the basic CAPTCHA (which is basically useless)
You will note that those posts were made by ACTUAL USERS.... they are not "non existant". The spammers registered accounts and posted messages.
If you just started the forum, I would suggest
1- delete the entire database
2- reinstall SMF in a new database and turn OFF registration until you want your site to actually be open.
3- read the SPAM FAQ in the wiki/manual before you open your site