wow, well you may want to cheack all your files to see if a hacker got in with a script
look for a file that is not yours, or not part of your site
*.txt / *.php in like images folder or other places
also, you have a firewall ?
there is much more then just above, if you dont know much how to get around ssh or tweaking your server. I'll advise you to hire a admin to find and fix the problem, before you get listed on spamhaus or other blacklist database