ISPs should block zombies (Score 1)

Can't an ISP detect if an IP address is sending out the *same* HTTP request several hundred times per second? I think that would be dirt simple to implement for an ISP (they could hash the request before comparing it so as not to invade precious privacy). There aren't any obvious legitimate reasons to be making that many requests, so I think its fair to assume that a machine doing so is participating in a DDoS and should have its upstream blocked.