I work for a small phone company. We have about 800 DSL customers. Last night one of our customers got denial of service attacked due to pissing someone off on Xbox Live. This caused our whole network to crash. We have 200Mb/s from our ISP for our customers and it was maxed out because of it. I isolated the destination address on our network and had the ISP make a rule in our router that took all the traffic sent to that IP address and redirected it to nowhere. This fixed the problem. So my question is are there any ways to prevent this? Our internet router connected to our ISP is a Cisco 4948E. I read online that Cisco IOS has a few ways to help prevent this? But I am not fluent in Cisco and our router is managed by our ISP so they would be making any changes to the router. Any ideas on how to prevent this in the future?