What is Layer 7?

Layer 7 refers to the application layer of the Open System Interconnection (OSI) Model. In Layer 7, is the layer users interact with directly. It’s where the actual content of applications and APIs is generated, delivered, and interpreted — things like web pages, API responses, and data exchanged between apps. From layer 7, data is passed along down the stack, and broken up into ‘packets’.

Understand the OSI Model

The OSI model is a conceptual model that characterizes and standardizes the communication functions of a telecommunication or computing system without regard to its underlying internal structure and technology. Its goal is to enable diverse communication systems to operate with one another, via standard communication protocols. 

Put more simply,the OSI model helps to standardize how different computer systems and applications interact with each other and exchange data.

What does Layer 7 do?

Layer 7, the Application Layer of the OSI model, involves the ways in which an application communicates with the network. Layer 7 functions as an essential ‘interface’ between the applications a user interacts with, and the underlying network its data travels through. 

As the top layer of the OSI model, layer 7 involves data processing just beneath the virtual surface of an application. Data is presented in a way that user-facing applications can actually use it. A common example is an HTTP request used to load a webpage. 

You can think of Layer 7 as the ‘translator’ for applications - it interprets data from lower layers and puts it in ‘readable’ formats for applications. 

Why is Layer 7 important?

Layer 7 of the OSI Model is important because it enables user-facing communication on the internet. It also provides another layer to enforce security policies and controls. Layer 7 is the interface between the network and user applications - it defines the protocols (HTTP, SMTP) that applications use to communicate with one another. 

Where does Layer 7 sit in the OSI Model? 

You can see in the diagram that layer 7 sits at the top of the OSI model. Each of the layers performs specific functions or activities to enable computer systems  to successfully communicate across a network.

What are layer 7 security risks?

Layer 7 security risks involve any attacks targeting the application layer of the OSI model, where web and API services live. Unlike lower-layer attacks that flood bandwidth, Layer 7 attacks exploit application logic and resource limits, often appearing as legitimate traffic. Common risks include DDoS attacks, HTTP floods, API abuse, SQL injection, cross-site scripting (XSS), and credential stuffing. These types of attacks are designed to disrupt services, steal data, or bypass authentication.

Because these attacks mimic real user behavior via fully formed requests, they are often undetectable with traditional network firewalls. Attackers may exploit poorly validated inputs, weak authentication, or misconfigured APIs to exfiltrate sensitive data or take down critical applications. 

Layer 7 DDoS attacks pose a real threat. From a volume standpoint, these can overwhelm computationally intensive services and processes, impacting performance, availability, and operational expenses.

How do layer 7 DDoS attacks work?

An application-layer DDoS attack is a malicious attempt to overwhelm web applications by exploiting Layer 7 of the OSI model. It targets specific application vulnerabilities to disrupt service availability.

Unlike network-layer attacks that flood infrastructure, application-layer incidents overwhelm specific application processes, consuming significant computing power. By mimicking legitimate user traffic and patterns, these attacks can maximize impact while requiring very little attacker bandwidth. These attacks require the most computing power of any of the DDoS attacks because they're fully formed requests. It's the most costly but can be the hardest to detect because it mimics legit traffic.

How can you protect against layer 7 attacks?

1. Implement JavaScript challenge mechanisms

Adding JavaScript challenges can effectively distinguish bots from legitimate users. These prompts analyze visitor behavior for automation indicators. If automation is detected, additional verification tests will be activated to confirm legitimacy before granting further access. Test these systems rigorously to avoid hindering legitimate customers.

2. Deploy advanced Next-Gen WAFs (Web Application Firewalls)

Next-Gen WAFs use application-specific rulesets to identify and block malicious traffic. Properly tuned WAFs can flag abnormalities in request complexity, geolocation, session management, input sizes, and more. Consider using cloud-based Next-Gen WAFs to leverage shared threat intelligence for faster attack detection.

3. Use IP reputation filtering

IP reputation databases maintain up-to-date botnet and malware IP lists. Web applications can automatically block traffic from known malicious sources by referencing these databases. Ensure the database remains updated frequently as botnet IP addresses change rapidly.

4. Implement rate limiting at the application level

Rate limiting enforces thresholds for traffic volumes and request complexity while blocking offenders. For example, you can set limits on API calls per IP, concurrent sessions per user, or database reads per minute. Granular limits help resist sudden spikes while preserving legitimate access.

5. Create intelligent CAPTCHA verification

Advanced bot management solutions, like Fastly Bot Management, offer slick solutions for CAPTCHAs. Fastly’s Dynamic Challenges, a feature of Bot Management, is an adaptive security feature that intelligently adjusts protection based on real-time analysis of incoming traffic, regardless of whether it’s hitting your web applications or mobile experiences. Best of all, it’s fully integrated with Private Access Tokens (PATs), so those users get frictionless access with invisible automatic verification behind the scenes. This enables Dynamic Challenges to automatically validate the legitimacy of traffic with PATs whenever possible, serve non-interactive challenges to traffic that looks legitimate, or use interactive challenges to thwart malicious bots. 

6. Configure browser integrity checks

Examine incoming traffic for consistent browser fingerprinting. Requests lacking legitimate browser characteristics can be selected for additional verification or blocked completely. Browser integrity checks help ensure traffic originates from authentic sources. 

7. Use machine learning traffic analysis. 

Machine learning techniques create precise models of normal versus abnormal traffic patterns. Continuously training these systems on updated data improves detection accuracy. Frequent retraining ensures the models adapt to evolving traffic trends.

8. Implement token-based request verification

Tokenized keys with strict expiration timeframes validate that each API call originates from your legitimate frontend. Attacks attempting to bypass the front end are blocked as they lack valid tokens. Tokens should match session details to prevent replay attacks and unauthorized requests. 

9. Use adaptive traffic segmentation

Segmenting traffic by risk profile lets you isolate suspicious flows for further analysis while preserving application resources for legitimate users. Update risk models frequently to ensure accuracy and reflect the latest threat intelligence. 

How Fastly can help

As attackers increasingly exploit vulnerabilities in Layer 7 business logic, you must employ an array of adaptive defense strategies. No single solution provides comprehensive protection, but combining proactive and reactive mitigation techniques at the edge can effectively counter application attacks before they overwhelm infrastructure. Intelligent capabilities like machine learning and behavior analysis are beneficial for keeping up with the growing sophistication of malicious botnets and stressor services.

Fastly's DDoS Protection , Next-Gen WAF and Bot Management offerings provide a powerful yet flexible approach for shielding your web properties and APIs. Backed by a global edge network, the solution offers deep visibility into traffic combined with rapid threat detection and mitigation capabilities. 

Here's how the platform helps your business stay ahead of these threats:

• Automatic mitigation of attacks: Fastly uses proactive techniques to automatically identify and neutralize DDoS attacks without requiring manual intervention. Threats are addressed immediately, minimizing disruption.

• Improved resilience: With Fastly’s solution, applications, and APIs maintain consistent performance and availability, even during high-volume attacks. This resilience ensures a swift customer experience for legitimate traffic.

• Dynamic detection and adaptive identification: Fastly continuously monitors incoming traffic, using advanced analytics to detect anomalous attack patterns instantaneously. Adaptive identification ensures the solution stays effective against evolving threats.

• Zero attack fees: Fastly doesn't charge for attack traffic, unlike many providers. You only pay for legitimate requests, keeping operational costs predictable and reducing financial strain during prolonged attacks.

• Integrated next-gen WAF: Fastly's next-gen WAF complements DDoS protection by identifying and blocking malicious web requests.

• Rapid mitigation: The platform reduces the impact of attacks on end users by mitigating threats in seconds.

• Versatile deployment: Fastly protects applications of all sizes with fast, upgradable defenses.

• Rate Limiting: Fastly allows administrators to set thresholds for the number of requests a user or IP address can make in a given time period.

Learn how Fastly can protect your applications, APIs, and microservices, ensuring your business stays secure and resilient to developing threats.