Nortel BSR222, Configuration, Page: 161 / 451

Chapter 10 Firewalls 161
Nortel Business Secure Router 222 Configuration — Basics
Figure 48 SYN flood
In a LAND Attack, hackers flood SYN packets into the network with a spoofed
source IP address of the targeted system. This makes it appear as if the host
computer sent the packets to itself, making the system unavailable while the target
system tries to respond to itself.
3 A brute force attack, such as a Smurf attack, targets a feature in the IP
specification known as directed or subnet broadcasting, to quickly flood the
target network with useless data. A Smurf hacker floods a router with Internet
Control Message Protocol (ICMP) echo request packets (pings). Since the
destination IP address of each packet is the broadcast address of the network,
the router broadcasts the ICMP echo request packet to all hosts on the
network. If there are numerous hosts, this creates a large amount of ICMP
echo request and response traffic. If a hacker chooses to spoof the source IP
address of the ICMP echo request packet, the resulting ICMP traffic not only
clogs up the intermediary network, but also congests the network of the
spoofed source IP address, known as the victim network. This flood of
broadcast traffic consumes all available bandwidth, making communications
impossible.