Dell PowerConnect B-RX BigIron RX Series Configuration Guide v02.7.02 - Page 1055

Chapter Protecting Against Denial of Service Attacks 34 In this chapter •Protecting against Smurf attacks 983 •Protecting against TCP SYN attacks 985 •Displaying statistics due DoS attacks 988 •Clear DoS attack statistics 988 In a Denial of Service (DoS) attack, a router is flooded with useless packets, hindering normal operation. The BigIron RX includes measures for defending against two types of DoS attacks, Smurf attacks and TCP SYN attacks. Protecting against Smurf attacks A Smurf attack is a kind of DoS attack where an attacker causes a victim to be flooded with ICMP echo (Ping) replies sent from another network. Figure 127 illustrates how a Smurf attack works. FIGURE 127 How a Smurf attack floods a victim with ICMP replies 1 Attacker sends ICMP echo requests to broadcast address on Intermediary's network, spoofing Victim's IP address as the source Attacker 2 If Intermediary has directed broadcast forwarding enabled, ICPM echo requests are broadcast to hosts on Intermediary's network Intermediary 3 The hosts on Intermediary's network send replies to Victim, inundating Victim with ICPM packets Victim The attacker sends an ICMP echo request packet to the broadcast address of an intermediary network. The ICMP echo request packet contains the spoofed address of a victim network as its source. When the ICMP echo request reaches the intermediary network, it is converted to a Layer 2 broadcast and sent to the hosts on the intermediary network. The hosts on the intermediary network then send ICMP replies to the victim network. BigIron RX Series Configuration Guide 983 53-1001810-01