Which of the following will help prevent smurf attacks?

A.
Allowing necessary UDP packets in and out of the network

B.
Disabling directed broadcast on border routers

C.
Disabling unused services on the gateway firewall

D.
Flash the BIOS with the latest firmware

Explanation:
A smurf attack involves sending PING requests to a broadcast address. Therefore, we can prevent

smurf attacks by blocking broadcast packets on our external routers.
A smurf attack is a type of network security breach in which a network connected to the Internet is
swamped with replies to ICMP echo (PING) requests. A smurf attacker sends PING requests to an
Internet broadcast address. These are special addresses that broadcast all received messages to
the hosts connected to the subnet. Each broadcast address can support up to 255 hosts, so a
single PING request can be multiplied 255 times. The return address of the request itself is
spoofed to be the address of the attacker’s victim. All the hosts receiving the PING request reply to
this victim’s address instead of the real sender’s address. A single attacker sending hundreds or
thousands of these PING messages per second can fill the victim’s T-1 (or even T-3) line with ping
replies, bring the entire Internet service to its knees.
Smurfing falls under the general category of Denial of Service attacks — security attacks that don’t
try to steal information, but instead attempt to disable a computer or network.