What Is a Layer 3 DDoS Attack?

A Layer 3 DDoS attack, also referred to as a network or protocol-based DDoS attack and/or volumetric DDoS, targets a specific network layer of the Open Systems Interconnection (OSI) model. This layer is responsible for routing data packets across different networks. These attacks exploit vulnerabilities in network protocols, such as Internet Protocol (IP), Internet Control Message Protocol (ICMP), and Address Resolution Protocol (ARP), to overwhelm a target’s network infrastructure with an excessive amount of traffic.

Layer 3 DDoS attacks are designed to exhaust the resources of network devices, such as routers, firewalls, and load balancers, by flooding them with an overwhelming volume of network packets. This flood of traffic consumes the available bandwidth, degrades network performance, and ultimately leads to a denial of service for legitimate users trying to access the targeted network or application.

Layer 3 DDoS attacks leverage various techniques to achieve their disruptive goals. Let’s take a closer look at some of the commonly employed methods:

ICMP flood: In an ICMP (Internet Control Message Protocol) flood attack, the attacker sends a massive amount of ICMP echo request packets to the target network. The target’s network devices, overwhelmed by the flood of incoming requests, struggle to respond to each one, leading to network congestion and performance degradation.

IP fragmentation: IP fragmentation involves sending fragmented IP packets to the target’s network. This technique takes advantage of the reassembly process that the target’s devices must perform to reconstruct the original packet. By overwhelming the target’s devices with an excessive number of fragmented packets, the attacker aims to consume their processing power and resources.

Smurf attack: In a Smurf attack, the attacker spoofs the source IP address of their ICMP echo request packets to the broadcast address of a target network. When the target network receives these spoofed packets, it broadcasts ICMP echo reply packets to all hosts in the network. With numerous replies flooding the network, it quickly becomes overwhelmed and unable to handle legitimate traffic.

DNS amplification: DNS (Domain Name System) attacks exploit the design of DNS servers that respond to queries with larger responses than the original request. This affects the DNS at Layer 7 (application layer). When the attacker sends a flood of DNS queries with spoofed source IP addresses of the victim, the attack traffic affects the victim’s network infrastructure at Layer 3 (network layer). As a result, DNS servers unwittingly send larger responses to the victim’s IP address, overwhelming their network capacity.

Layer 3 DDoS attacks pose a significant challenge for organizations, as they directly target the underlying network infrastructure. However, several measures can be implemented to mitigate the impact of Layer 3 DDoS attacks. Here are some effective strategies:

Network traffic filtering: Implementing network traffic filtering mechanisms can help mitigate the impact of Layer 3 DDoS attacks. By analyzing incoming traffic and filtering out malicious packets, organizations can prevent the attack traffic from reaching their network infrastructure. This can be achieved through the use of firewalls, intrusion detection systems (IDS), and intrusion prevention systems (IPS) that are capable of detecting and blocking suspicious or anomalous traffic patterns.

Rate limiting and traffic shaping: Rate limiting and traffic shaping techniques can be employed to control the flow of network traffic and prevent the overwhelming volume of packets associated with Layer 3 DDoS attacks. By setting limits on the number of packets or connections allowed per second, organizations can effectively manage network resources and prevent congestion caused by the attack traffic.

Blackhole routing: Blackhole routing, also known as null routing, involves redirecting all traffic destined for a specific IP address or network to a “black hole.” This effectively drops all incoming traffic directed toward the targeted network, including the malicious packets associated with Layer 3 DDoS attacks. By implementing black hole routing on the network infrastructure, organizations can minimize the impact of the attack and preserve their network resources for legitimate traffic.

Traffic anomaly detection via cloud scrubbing: Implementing traffic anomaly detection systems can help identify and respond to Layer 3 DDoS attacks in real time. These systems analyze network traffic patterns and behavior to detect any deviations from normal traffic patterns. When an anomaly is detected, the system can trigger automated mitigation measures, such as traffic rerouting, rate limiting, or traffic filtering, to protect the network infrastructure from the attack.

Content delivery networks (CDNs): Deploying a Content Delivery Network (CDN) can help mitigate the impact of Layer 3 DDoS attacks by distributing the network traffic across multiple geographically dispersed servers. CDNs use caching and load balancing techniques to efficiently deliver content to users, reducing the strain on the origin server and making it more resilient to DDoS attacks. By diverting the attack traffic to the CDN’s distributed infrastructure, organizations can mitigate the impact on their network and ensure uninterrupted service availability.

Collaborative defense mechanisms: Collaborative defense mechanisms involve sharing threat intelligence and coordinating responses among multiple organizations. By participating in collaborative defense initiatives, organizations can benefit from a collective pool of knowledge and resources to better detect, analyze, and mitigate Layer 3 DDoS attacks. Sharing information about attack signatures, traffic patterns, and mitigation techniques can help organizations proactively defend against such attacks and minimize their impact.

Layer 3 DDoS attacks pose a significant threat to network infrastructure, often resulting in service disruptions and financial losses for organizations. Understanding these attacks and implementing appropriate mitigation strategies are crucial to ensure network resilience and uninterrupted service availability. Through measures such as cloud scrubbing, network traffic filtering, rate limiting, traffic shaping, and collaborative defense mechanisms, organizations can effectively mitigate the impact of Layer 3 DDoS attacks and protect critical assets from malicious actors.

Staying proactive and continuously monitoring network traffic for anomalies is key to promptly detecting and responding to Layer 3 DDoS attacks. By investing in robust cybersecurity measures and staying informed about emerging attack techniques, organizations can stay ahead in the ever-evolving landscape of cyberthreats.