Traditional DDoS of course is when an attacker uses thousands of centrally controlled zombie machines to direct millions of packets at a single destination. Most web servers shrivel up and die when subjected to that much attention. According to Barrett even the upstream infrastructure cannot withstand some of these attacks. The firewalls, routers, sometimes even the ISP go off line. A recent new technique is for the zombies to all perform DNS look-ups causing a failure of the DNS server for the target to die, effectively taking down a site without even hitting it directly.

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