I doubt it's a DDoS attack on a site that is only a month old. Maybe a misconfiguration, seo issue, or some other site getting DDoS'ed on your shared server. I would recommend that you upgrade from shared hosting to VPS, see if that solves the issue, if not then I would spend money on hiring a good server admin to check any config issues.
A few not in the list,
I've updated the xml file.
We all have seen spammers using temp email services to register and spam, and I really hate it. Here's a list of a few temp email services. Some of the domains have expired, let's keep the list updated and clean.
This feature is really needed, one of our rouge staff member mass edited topics to "ABCD" now there is no way of going back except restoring the database by which we will lose hundreds of new registrations and posts.