ISA Server will block all HTTP requests from a specific source IP address for one minute because the number of HTTP requests per minute from this source IP address exceeded the configured limit.
The number of HTTP requests per minute from a specific source IP address exceeded the configured limit. This IP address may belong to a host that is infected by a worm and is attempting to propagate the worm by scanning the network to find other vulnerable hosts.
Clean the client computer with this IP address if it is infected.
See the product documentation for more information about ISA Server flood resiliency.