What Is an Application Layer DDoS Attack?

Protect your organization from an Application Layer Denial of Service (DDoS) attack with Perimeter 81’s comprehensive cloud network security solution, easily deployed across hybrid networks.

Perimeter 81

30.07.2024

5 min read

What Is an Application Layer DDoS Attack?

An Application Layer DDoS attack, also known as a Layer 7 attack, targets the top of the OSI model where HTTP GET and POST requests happen. These attacks consume server resources and network resources, making them highly effective. 

Traditional cybersecurity solutions often miss them, leading to downed websites or networks. 

Attackers use request floods, exploit application vulnerabilities, launch application-specific attacks like XML-RPC floods, and take advantage of zero-day vulnerabilities.

Types of Application Layer Attacks

The rise of insecure IoT devices has given attackers nearly unlimited resources to launch a sophisticated Application Layer DDoS attack. 

Here are some common types:

• SQL Injection: Attackers inject malicious SQL code into website input fields. Without proper input validation, they can change SQL queries, potentially accessing databases or affecting their integrity.
• Cross-Site Scripting (XSS): Attackers introduce malicious code into web pages that other users read.
• Cross-Site Request Forgery (CSRF): Attackers trick users into unknowingly performing actions on a website, like changing account settings or making transactions.
• Buffer Overflow: Exploiting vulnerabilities in data buffer handling, attackers can overwrite memory, causing crashes or remote code execution.
• Directory Traversal: Attackers aim to access files and directories outside an application’s scope, potentially accessing sensitive server files if inadequately protected.
• API Attacks: As APIs increasingly facilitate data interchange between apps, attackers may exploit API vulnerabilities for unauthorized data or service access.

The Dangers of Application Layer Attacks

A successful Application Layer DDoS attack can shut down a website and its services, preventing businesses from taking online orders and frustrating customers. 

If a public administration website goes down, it may deny citizens critical services.

Attackers often use botnets to modify their requests, adapting to any defensive measures taken by website operators. Organizations trying to identify and respond to these evolving patterns manually will likely be overwhelmed. 

The financial implications can be significant for businesses relying on their website to drive sales. A site hit by frequent attacks and ongoing outages will see a long-term decrease in legitimate traffic.

Challenges in Mitigating Application Layer Attacks

Distinguishing between attack traffic and normal traffic proves difficult, especially when a botnet performs an HTTP Flood attack. Mitigating an Application Layer DDoS attack poses unique challenges. 

Each bot makes seemingly legitimate requests, so the traffic appears normal.

Adaptive strategies are necessary, including limiting traffic based on regularly fluctuating rules. A properly configured WAF can mitigate bogus traffic from an origin server, reducing the attack’s impact.

Network administrators can mitigate attacks like SYN floods or NTP amplification by efficiently dropping traffic if the network has sufficient bandwidth. However, most networks can’t receive a 300Gbps amplification attack or properly route and serve the volume of requests an L7 attack generates.

Strategies to Defend Application Layer Attacks

Mitigating an Application Layer DDoS attack can be difficult, as the traffic often mimics legitimate user behavior and goes undetected until it’s too late. 

Here are some strategies to defend against these attacks:

Implement Multi-layered DDoS Protection

Attackers constantly find new ways to make websites unavailable and exploit vulnerabilities. Preventing these attacks requires more than just increasing bandwidth or using standard firewalls. 

A comprehensive, multi-layered protection approach with specialized defenses against application-layer attacks is necessary.

To defend against modern DDoS threats, your solution must:

• Be scalable
• Have built-in redundancies
• Monitor traffic
• Detect business logic flaws
• Effectively manage vulnerabilities

Apply Rate Limiting

Rate limiting prevents Application Layer DDoS attacks by restricting traffic sent to a network or server within a specified time frame. The system drops or delays excess traffic when it reaches the limit.

Implement rate limiting at the network, application, or DNS layers. Configure it carefully to avoid blocking legitimate traffic.

Enforce rate limits for API endpoints to prevent API abuse and mitigate DDoS risks targeting specific endpoints. Rate limiting alone may not fully defend against sophisticated application layer attacks.

Create a DDoS Attack Threat Model

A DDoS attack threat model helps identify and analyze potential risks to your online service or website. 

Here’s a structured approach to create one and defend against an Application Layer DDoS attack:

1. Inventory your web assets: Create a comprehensive database of all web assets you want to protect, including network details, protocols, domains, applications, and versions.
2. Identify potential attackers: Define potential attackers who might target your assets, such as hacktivists, competitors, or nation-state actors. Understand their motives and capabilities.
3. Determine attack vectors: Identify various attack vectors an attacker could use, such as UDP flooding, SYN flooding, or HTTP flooding, to develop appropriate defense strategies.
4. Analyze the attack surface: Examine your network topology, hardware infrastructure, and software stack to understand potential vulnerability points attackers could exploit.
5. Evaluate risk level: Assess the probability, potential impact, and likelihood of detecting and mitigating each attack vector to prioritize mitigation efforts and allocate resources effectively.

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Best Practices for Preventing Application Layer Attacks

Here are some best practices for preventing Application Layer DDoS attacks, the most common attack type against web applications with 37.1%:

• Prepare for surges: Ensure your infrastructure can withstand sudden traffic spikes. Consider using CDN services with globally dispersed networks and redundant resources to handle increases effectively.
• Recognize warning signs: DDoS attacks have symptoms like spotty intranet connectivity, intermittent website shutdowns, and internet disconnections. These signs can be similar to other issues like viruses or slow internet connections.
• Implement black hole routing: Configure routers or switches to send malicious traffic to a null interface, dropping it before reaching the target network or server. Use black hole routes to block traffic from specific IP addresses or subnets identified as attack sources.

Create a Bulletproof Security Strategy with Perimeter81

Leverage Perimeter81’s network security and threat mitigation expertise to safeguard your organization against evolving DDoS threats. Perimeter81 offers comprehensive solutions to protect against Application Layer DDoS attacks. 

Our platform integrates advanced security features like next-generation firewalls, rate limiting, and bot mitigation to detect and block malicious traffic. 

Join a 15-minute demo to learn how our converged cloud-based solution can help you quickly connect and secure your network.

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