Restricting multiple HTTP requests?

We had a minor issue with one of our production servers the other day. Looks like a PDF reader client went a bit bananas after a timeout and started sending multiple requests for the same pdf over a period of time.

Sadly after a while this consumed all of the HTTP threads which impacted other users trying to access the server over the course of a few hours.

We have firewalls etc. in place to protect against a DoS, but are at a threshold level much higher than a GET every few seconds for a large file from one IP address.

Is there anything that can be done in Domino to prevent one user/IP address from grabbing all the http threads?

TIA - Rufus.