Allied Telesis AT-S63 - Manual (Page 381)

AT-S63 Management Software Menus Interface User’s Guide
Section II: Advanced Operations 381
Smurf Attack This DoS attack is instigated by an attacker sending a ICMP Echo (Ping)
request containing the network’s IP broadcast address as the destination
address and the address of the victim as the source of the ICMP Echo
(Ping) request. This overwhelms the victim with a large number of ICMP
Echo (Ping) replies from the other network nodes.
A switch port defends against this form of attack by examining the
destination IP addresses of ingress ICMP Echo (Ping) request packets
and discarding those that contain the network’s IP broadcast address as a
destination address.
Implementing this defense requires that you provide an IP address of a
node on your network and a mask. The switch uses the two to determine
the broadcast address of your network.
This defense mechanism does not involve the switch’s CPU. You can
activate it on as many ports as you want without having it negatively
impact switch performance.
Land Attack
In this attack, an attacker sends a bogus IP packet where the source and
destination IP addresses are the same. This leaves the victim thinking that
it is sending a message to itself.
The most direct approach for defending against this form of attack is for
the AT-S63 management software to check the source and destination IP
addresses in the IP packets, searching for and discarding those with
identical source and destination addresses. But this would require too
much processing by the switch’s CPU, and would adversely impact switch
performance.
Instead, the switch examines the IP packets that are entering and leaving
your network. IP packets generated within your network and containing a
local IP address as the destination address are not allowed to leave the
network, and IP packets generated outside the network but containing a
local IP address as the source address are not allowed into the network.
In order for this defense mechanism to work, you need to specify an uplink
port. This is the port on the switch that is connected to a device, such as a
DSL router, that leads outside your network. You can specify only one
uplink port.
Note
If the switch is not connected to a device that leads outside your
network, you should not use this defense mechanism.
You also need to enter the IP address of one of your network devices as
well as a mask which the switch uses to differentiate between the network
portion and node portion of the address. The switch uses the IP address
and mask to determine which IP addresses are local to your network and