Not to sound like a shill, but this is exactly that: http://www.arbornetworks.com/products/arbor-cloud . Again, most ISPs worth their salt already implement PeakFlow in their backbone IP networks to catch and control large scale DDoS events, but at multi-gigabit levels - setting the threshold just low enough to ensure that DDoS attacks don't wipe-out their backbones, a level that is much higher than any single customer link bandwidth. Today, they (we) are beginning to offer these services (based on BGP, threat intelligence shared between ISPs and Security Consultancies, and "live" feedback from CPE-Probes like Pravail at customer sites) and they do work for the most part. The only downside (other than pricing - which is kinda steep) is the fact that it is a defensive mitigation approach - you BGP-blackhole the bad traffic in the customer-side ISP backbone, not the source. It's not going to eliminate the ever-growing and extremely long list of asshats (including sovereign state actor-asshats) that initiate these kinds of attacks, but it can and does, currently, mitigate the vast majority of them. So, yay-ish.