Figure 1 shows different Denial of Service attacks and shows how the resource overload affects the data. Figure 2 shows an attacker sending a ping of death packet to a host.  The malformed packet overloads the host and renders the host unresponsive. Figure 3 demonstrates a syn flood attack.  In this figure the attacker is sending multiple syn packets to a web server.  The attacker does not complete the transaction and when a valid user sends a syn request, the server is unavailable. Figure 4 shows an attacker connected to many servers acting as zombies or agents for a denial of service attack.  The agents launch the attack on a single host and render it unavailable. Figure 5 shows an attacker connected to a router acting as a smurf amplifier.  The amplifier tells many zombie computers to send an ICMP reply to a single host.  This overwhelms the destination.