limit number of HTTP requests on IIS 6.0

Is there a way I can limit the number of HTTP requests based on IP
addresses 
on IIS 6.0? Our system experienced a "denial of service" attack due to
faulty 
configuration on the requesting side, within 30 minutes there were about 
25000 HTTP requests to our system. I am hoping to find a way to prevent it

from happening again, basically something that says limit the number of
HTTP 
requests from the same IP address to N requests per minute. Any help is 
appreciated. Thanks in advance.