What is a Positive Security Model?
A Positive Security Model is a proactive security approach that explicitly allows only known good traffic, behaviors, or services, blocking everything else by default (“default deny”). In the context of API security, it means specifying the permitted API endpoints, headers, and request parameters.
In contrast, a Negative Security Model works by blocking known bad behaviors, allowing everything else by default.
By focusing on what is allowed, the Positive Model offers better protection against zero-day attacks, unknown threats, and sophisticated adversaries.
Let’s break down how it works, its advantages, and best practices for implementation.
What are the Key Benefits of the Positive Security Model?
The Positive Security Model is proactive. It allows only approved behaviors and blocks everything else.
Here’s a more detailed breakdown of why positive security is important:
1. Protection Against Zero-Day Attacks – Unlike negative models, which require signatures or patterns to identify threats, the positive model blocks anything not recognized. This includes unknown or zero-day exploits, offering inherent protection.
2. Reduced False Positives: – Whitelisting in the Positive Security Model cuts false positives by allowing only approved actions, reducing noise and helping security teams focus on real threats.
3. Reduced Attack Surface – By limiting actions to only those that are explicitly approved, the system inherently prevents lateral movement, command injection, or data tampering that might otherwise exploit weak points.
4. Minimized Human Error – Misconfigurations often cause breaches. The positive model blocks anything not explicitly allowed—reducing that risk.
5. Stronger Security for Sensitive Applications – This model is well-suited for applications that handle highly sensitive data because it ensures that only trusted interactions are permitted.
6. Improved Policy Clarity and Accountability – Organizations are required to define what should be allowed, encouraging a well-documented and better-understood policy environment. This brings more visibility and operational discipline.
7. Simplified Security Management – Once the initial whitelist is established, managing the Positive Security Model can be simpler than maintaining a blacklist in a Negative Security Model, according to 42Crunch.
Positive vs. Negative Security Model: A Comparison
Let’s compare both models across key areas:
Definition & Philosophy
A Positive Security Model follows a “default deny” approach — only explicitly allowed behaviors are permitted. In contrast, a Negative Security Model works on “default allow,” blocking only known malicious patterns.
Implementation
Positive models use allowlists and require upfront knowledge of valid traffic. Negative models rely on blacklists and threat signatures, making them easier to deploy but more reactive.
Security Effectiveness
Positive models offer strong protection against unknown and zero-day threats by rejecting anything unfamiliar. Negative models can miss such threats but typically result in fewer false positives.
Maintenance
Positive models need more manual updates and tuning as application behavior evolves. Negative models are easier to automate but demand constant rule updates.
Use Cases
Positive models are ideal for high-security APIs, critical infrastructure, and regulated industries. Negative models fit better in fast-moving environments with broader access requirements.
Pros & Cons
Positive models provide stronger security but require more effort. Negative models offer flexibility and faster deployment but are more vulnerable to unknown threats.
Summary: Positive vs. Negative Model
| Factor | Positive Model | Negative Model |
| Default Stance | Deny by default – only allow what’s known to be safe. | Allow by default – block only what’s known to be bad. |
| Setup Complexity | High – must know all valid use cases. | Moderate – focus on known threats. |
| Protection Against Zero-Day Attacks | High – blocks unknown behaviors by default. | Low – allows unknown unless they match a threat pattern. |
| False Positives | More likely (may block legitimate behavior). | Less likely (but more prone to false negatives). |
| False Negatives | Low – unknowns are blocked. | High – unknown or unlisted threats may pass through. |
| Maintenance Overhead | High – every new valid behavior must be added manually. | Continuous – needs regular updates to block emerging threats. |
| Endpoint Protection | Allows only signed/trusted applications. | Detects/blocks known malware signatures. |
| Access Control | Role-based or attribute-based access; users only get specific rights. | Reactive blacklisting of users/IPs based on behavior. |
How AppTrana WAAP Leverages the Positive Security Model for API Protection
AppTrana WAAP (Web Application and API Protection) applies a Positive Security Model to protect APIs from day one. It does this through advanced capabilities such as API discovery, vulnerability scanning, and penetration testing.
One of the key advantages of AppTrana WAAP is its ability to automate the creation and enforcement of positive security policies for APIs. Even in the absence of formal documentation like Swagger or Postman, AppTrana simplifies adoption by first discovering all active APIs across your environment—including undocumented ones. It then conducts API vulnerability scanning and penetration testing to assess their risk profile and expected behavior.
Based on these insights, AppTrana generates precise positive security policies that define which API calls, parameters, and behaviors are permitted, blocking anything outside this predefined scope. In addition to its whitelisting approach, AppTrana also employs a negative security model to detect and block known threats like SQL injection, XSS, and brute-force attacks, offering a dual-layered defense strategy.
For teams lacking formal API documentation, AppTrana further supports the process by automatically generating Swagger files and enabling the managed services team to create Postman files for critical APIs. This holistic approach enables organizations to enhance API protection, reduce the attack surface, and implement positive security models effectively and efficiently.
