Traffic from unknown URL

Looking for a little help.

My Colocator contacted me about excessive traffic on the server. After monitoring for a few hours, it appears my server is getting hits based on a domain name that I don't have. It's like someone is pointing a subdomain at my servers IP address and hammering it for requests.

Any idea how I can get it to stop?

you need to check that with your server provider or some experienced system admin as all depends on the traffic type, data.....