Hits from one IP address taking our site down

Thank you all for your ideas and suggestions. Yes, we block using ASM GeoLocation Enforcement. The logs do not indicate that the user was able to access our site. I suppose it might have simply been an overload to our server at the same time that the one IP Address was hitting several times each second. We have actually had that same type of hit in the past, but it never took the site down. Unless it happens again, I will chalk this up to coincidence of attack and server overload. I appreciate this forum very much. Thank you!