An administrator is instructed to disable IP-directed broadcasts on all routers in an organization. Which of the following attacks does this prevent?
A. Pharming B. Smurf C. Replay D. Xmas
Answer: B
Explanation: 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 Internet connection with ping replies, bringing their 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.
By disabling IP-directed broadcasts on all routers, we can prevent the smurf attack by blocking the ping requests to broadcast addresses.