What is Smurf DDoS Attack
A Smurf attack is a distributed denial-of-service (DDoS) attack that exploits Internet Protocol (IP) broadcast addresses and spoofed source addresses to overload a targeted device or network with bogus traffic. It allows an attacker to amplify the amount of traffic generated, with the goal of overwhelming the target’s network or device.
How a Smurf DDoS Attack Works
A Smurf attack uses crafted Internet Control Message Protocol (ICMP) echo request packets to overwhelm a targeted device. The size of the ensuing DDoS attack is measured in packets per second (PPS).
Here are the technical details of how a standard Smurft attack works:
- The attacker spoofs the victim’s IP address as the source IP and sends ICMP echo requests (pings) to the network’s broadcast address.
- Routers on the network receive the ICMP echo request and flood it to all hosts per the broadcast address destination.
- Each host that receives the ICMP request replies back to the source IP with an echo reply packet containing the target’s IP address.
- All the responses are sent back to the victim, overwhelming it with traffic and causing a denial of service (DoS).
The attacker’s initiating ping is multiplied by all the hosts responding, creating an amplification effect that can generate floods of traffic directed at the target’s network or device(s).
What are the Characteristics of a Smurf Attack
Some key characteristics of the Smurf DDoS attack include:
- Reflective – The responses are sourced from third-party systems, hiding the attacker’s identity.
- Amplified – Exploits ICMP echo replies for traffic multiplication.
- Layer 3 – Operates at the network layer, flooding victims with ICMP traffic.
- Distributed – Involves many responding hosts spread across networks.
- Difficult to Stop – Trivial to initiate and challenging to block all vulnerable networks.
Other well-known protocol attacks include: SYN flood, Ping Flood, Fraggle Attack.
Amplification Factor
The amplification factor of the attack refers to how much traffic is generated compared to the volume of packets sent by the attacker. Typical amplification factors observed in Smurf attacks include:
- 20X-70X – If the network has 20-70 hosts, each ICMP echo reply packet sent to the victim multiplies the traffic by that factor.
- >100X – Very large networks with hundreds, or thousands, of hosts can yield amplification of over 100 times.
Due to the amplification factor, even a low-bandwidth attacker can yield attacks exceeding 1Gbps or more by exploiting a large network.
History of Smurf Attacks
Smurf attacks emerged in the late 1990s as a new vector for DDoS. Some major historical events involving Smurf attacks include:
- 1996-1999 – First observed attack, quickly becoming a popular DDoS technique.
- 2000 – Major Smurf attacks made headlines after taking down sites like eBay, Amazon, and more.
- 2001 – CERT advisory officially documents the Smurf attack method.
- 2003 – FTC charges offenders for launching Smurf attacks against business competitors.
While improved Internet infrastructure configurations have mitigated their effectiveness, Smurf DDoS capabilities still persist today.
Defending Against Smurf Attacks
There are several key measures that can be taken by both network operators and sites to defend against Smurf DDoS attacks:
- Disabling Directed Broadcasts – Routers should drop packets with directed broadcast destination addresses.
- Filtering ICMP – Where possible, block outbound and rate limit inbound ICMP.
- Firewall Rules – Add specific firewall policies to block Smurf-like patterns.
- Switch Port Security – Limit number of MACs per switchport or virtual local area network (VLAN) to prevent overflows.
- DDoS Mitigation – Use upstream or on-premises DDoS mitigation services that can detect and filter out attack traffic.
While Smurf attacks can be challenging to fully eliminate, adopting these protections significantly reduces the DDoS threat.
The Evolution of the Smurf DDoS Threat
Though their popularity has declined, Smurf attacks are still relevant today and impact the following:
- IP-Enabled Devices – The growth of the Internet of Things provides new devices to target.
- Public Cloud – Shared infrastructure increases risk of reflection attacks.
- IPv6 – Introduces new reflective attack vectors via multicast addressing.
- Script Kiddies – Launching Smurf attacks is trivial for novice attackers.
Proper network hardening is crucial to manage this persistent DDoS threat.
Impact of Smurf DDoS Attacks
The effects of a Smurf attack on targeted organizations and networks include:
- Service outages – Websites, applications, and infrastructure may be knocked offline completely.
- Loss of revenue – Downtime translates directly into lost sales and revenue.
- Reputational harm – Users lose trust after experiencing site outages.
- Productivity loss – Staff are unable to perform duties during outages.
- Costly mitigation – Extensive provider filtering or scrubbing services are required.
Mitigate and Protect from Smurf DDoS Attacks with Imperva
Implementing a DDoS protection solution and web application firewall (WAF) can filter out and manage high volumes of malicious traffic from a range of attacks, like a Smurf DDoS attack.
Imperva DDoS Protection proxies all incoming traffic to block DDoS attacks from reaching your origin servers.
Imperva secures websites, networks, DNS servers, and individual IPs from network and application layer DDoS attacks. The cloud-based service keeps business operations running at high-performance levels, even during an attack.
