Layer 7 attacks are the new hotness in DDoS.  If you have a big enough botnet (either conventional botnet, or hijacked browsers), you can do them, and they&#x27;re often quite effective.<p>Fundamentally, layer 3&#x2F;4 are usually amplification.  Those are still effective, and very efficient for the attacker, but they will someday (5y? 10y?) be blocked by closing up sources amplification.  Address spoofing address at layer 3&#x2F;4 might get addressed by BCP 38, Vixie&#x27;s good fight, etc., but not holding my breath.<p>By the time all that happens, attackers will have moved on to layer 7 attacks.  Those can target the weakest parts of your stack, and with a large botnet, even the act of blocking the IPs in the wrong place can add enough overhead to hurt.  With a huge botnet of hijacked browsers, blocking everyone affected becomes a DoS vector in itself, since some of those are your own legitimate attacks.<p>The big problem for DDoS mitigation is that this requires much deeper knowledge of the protected application.  It&#x27;s hard to just put a box inline, or an unmodified cloud service, and have it block the attacks.  There&#x27;s both good science and great engineering to be done, by developers, platform vendors, and specialty anti-DDoS providers, to block this emerging kind of attack.