Why Is It Called A SMURF Attack?

A SMURF Attack is a form of denial-of-service (DoS) that occurs when an attacker sends ICMP Echo Request packets to broadcast addresses on the Internet. “SMURF” stands for “Smurfing IP Denial of Service attacks using Random Fragments.” The name derives from the original use of this type of attack by hackers who sent ICMP echo request packets to a victim’s network, with source address spoofed as belonging to a victim’s ISP. This would cause all hosts on that network to respond simultaneously and overload it.

How Smurf Attacks Work

A smurf attack occurs when an attacker sends ICMP echo requests from spoofed source addresses to a network’s broadcast address. This causes all hosts within that subnet to respond, which then creates a flood of responses back toward the real sender’s IP address – effectively taking down that machine or router. In this type of attack, multiple ISPs are used for reflection and can make it much larger in scale than other types of DoS attacks.

There are two different kinds of Smurf attacks. The first is an amplification attack that uses ICMP to amplify DDoS traffic by sending a spoofed echo request with the source address set as your victim’s IP address, which causes all hosts on their network to respond simultaneously. Since this type of attack sends only one packet but receives multiple responses, it amplifies the size of the attack.

The second type is a reflection attack, which sends echo requests from spoofed addresses to network prefixes that are routed with BGP through routers on different networks and then back to your victim’s location – this means you can reflect an attack of multiple ISPs at once before directing them toward your target. This is why the second type of Smurf attack can be much larger in scale and still work.

How to Defend Against Smurf Attacks

To protect your company against both types of smurf attacks, you should configure access lists on all border routers that block directed broadcast traffic originating from outside your network or initiating inside your network but destined for an IP address outside your network.

Do not allow ICMP echo requests from the Internet to your internal networks.
If it is necessary for hosts on a network to respond to pings, configure routers so they will only reply if the incoming packet’s source address appears to be a host belonging to that same subnet. This can be done by using access lists.
Block all ICMP echo requests with an access list, to prevent hosts from responding. This is not really a solution but only prevents the network’s users from being directly affected by Smurf attacks.
Configure routers so they will not forward broadcast packets at all. This can be done using ACLs on Cisco IOS routers and firewalls with built-in broadcast-blocking capabilities.

What is a Ping of Death?

A ping of death is an attempt to overwhelm a target with ICMP Echo Requests, causing loss of service while a Smurf attack is a form of denial-of-service (DoS) that occurs when an attacker sends ICMP Echo Request packets to broadcast addresses on the Internet.

The attackers send out a large number of ICMP echo requests to the broadcast address on each network from spoofed source addresses. This causes all hosts within that subnet to respond, which then creates a flood of responses back toward the real sender’s IP address – effectively taking down that machine or router.

How is a Smurf attack different from a Ping flood?

A ping flood is an attempt to overwhelm a target with Ping packets, causing loss of service while a Smurf attack is a form of denial-of-service (DoS) that occurs when an attacker sends ICMP Echo Request packets to broadcast addresses on the Internet.

What is meant by “fragmentation attack” in the context of Smurf attacks?

A fragmentation attack is an attempt to overwhelm a target with ICMP Echo Requests, causing loss of service while a Smurf attack is somewhat similar to ping floods, as both are attempts to overwhelm a target with ICMP Echo Requests, causing loss of service.

This causes all hosts within that subnet to respond, which then creates a flood of responses back toward the real sender’s IP address – effectively taking down that machine or router.

Conclusion

In Smurf Attack, attackers send out a large number of ICMP echo requests to the broadcast address on each network from spoofed source addresses. This causes all hosts within that subnet to respond, which then creates a flood of responses back toward the real sender’s IP address – effectively taking down that machine or router. Smurf attacks can be prevented by configuring access lists on all border routers that block directed broadcast traffic originating from outside your network or initiating inside your network but destined for an IP address outside your network.