Step one: Back up the entire site.
Step two: Delete the entire directory where the site existed.
Step Three: Restore your site from your most recent backup prior to the symptoms (not the one you just created in step one above!) If you KNOW that this issue first arose on November 10, tell the web host to restore your site from the backup made on the night of November 9.
Step Four: Change the current FTP and general website passwords.
If your web host says they do not have a backup, then you need a new web host.