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Analyzing DAST Methods: Quick and Shallow vs In-Depth Scans

June 7, 2023
Senad Čavkušić

Introduction

Dynamic Application Security Testing (DAST) is a crucial component in fortifying web applications against potential vulnerabilities. By taking a proactive stance, DAST systematically detects and addresses security flaws. Employing a black-box testing methodology, it scrutinizes the application from an external perspective, focusing on exposed interfaces without relying on internal source code knowledge. Through simulated cyberattacks, DAST diligently monitors application responses, exposing exploitable vulnerabilities like Cross-Site Scripting (XSS), SQL Injection, and Security Misconfigurations. The scanning process encompasses two distinct categories: rapid (or shallow) scans and intensive (or in-depth) scans. By delving into these approaches, we gain a comprehensive understanding of their unique attributes, advantages, and limitations.

Rapid Scanning: A Preliminary Line of Defense

Rapid scans, sometimes referred to as lightweight or shallow scans, provide a quick yet effective assessment of an application’s security posture. These scans work by rapidly crawling the application and testing for common, surface-level vulnerabilities. They are typically employed during the initial phases of the Software Development Life Cycle (SDLC) or as part of continuous integration/continuous deployment (CI/CD) in DevSecOps environments.

Rapid scans offer notable advantages in terms of speed and efficiency. Their swiftness enables a prompt security feedback loop, facilitating quick remediation and reducing the likelihood of vulnerabilities making it into production. Furthermore, their non-intrusive nature ensures minimal impact on system performance, making them well-suited for regular and frequent testing in agile development contexts.

However, it is important to recognize the limitations of rapid scans. Due to their focus on speed, they may provide a less exhaustive assessment, potentially overlooking complex, nested, or multi-step vulnerabilities that require a deeper understanding of the application’s behavior. Moreover, rapid scans may not comprehensively test all potential attack vectors, as they often prioritize higher-level, easily accessible interfaces.

To achieve a comprehensive security posture, it is crucial to supplement rapid scans with intensive scans. By combining the two approaches, organizations can leverage the efficiency of rapid scans while addressing the shortcomings through in-depth assessments. This balanced approach ensures that both the speed and thoroughness required for robust security are achieved.

Intensive Examination: The Deep-Dive Approach

Intensive scans, also known as deep or exhaustive scans, offer a far more thorough and comprehensive exploration of an application’s security landscape. This methodology involves an in-depth assessment of the application, probing parameters, analyzing responses, and validating potential vulnerabilities in detail. Techniques employed in this method often include advanced fuzzing, path traversal checks and analysis of business logic vulnerabilities.

The primary advantage of intensive scans is their thoroughness. They are capable of uncovering complex, multi-step vulnerabilities that rapid scans may miss, providing a detailed and comprehensive view of the application’s security standing. As a result, intensive scans are particularly beneficial for applications with high-security requirements, complex architectures, or those processing sensitive data.

Nonetheless, the exhaustive nature of intensive scans presents its own challenges. These scans are time and resource-intensive, often less feasible in fast-paced, agile environments. Their thoroughness can also lead to an increased number of false positives, requiring additional resources to analyze and validate the results. Furthermore, their invasive nature may disrupt regular operations or cause performance degradation, making them less suited for live or performance-sensitive systems.

How to choose the best approach

In the landscape of application security testing, both rapid and intensive scans serve indispensable roles. The decision between them should hinge upon a careful consideration of several factors including risk profile, development pace, resource availability, and the complexity of the application.

Rapid scans serve as a valuable preliminary measure, swiftly identifying and resolving common vulnerabilities during the early development stages. On the other hand, intensive scans deliver a comprehensive security audit, offering an invaluable layer of assurance for high-risk applications or prior to deployment.

A balanced and effective security strategy often leverages both approaches. Employing rapid scans early and often, followed by intensive scans at strategic points, can provide a layered and robust defense, delivering both speed and depth in your application security testing protocol.

The frequency and timing of these scans should align with the rhythm of your development cycle and the specific characteristics of your application. For instance, after the integration of new features or significant code changes, a rapid scan can provide immediate feedback to developers. This early detection reduces remediation costs and time, and prevents security debt from accumulating in the codebase.

Following the rapid scan, intensive scans can be scheduled at key milestones, such as before major version releases or after a significant architectural change. This in-depth scrutiny assures stakeholders that more intricate vulnerabilities have not been overlooked, thereby providing a solid security foundation for the application.

Apart from the scheduled scans, it’s worth noting that an agile DAST strategy should also allow room for unscheduled, trigger-based scans. These can be triggered by events such as the discovery of a new common vulnerability, a significant increase in traffic, or the release of a new version of a third-party component that an application relies on.

While integrating both rapid and intensive scans into your DAST strategy, it’s also important to remember the role of false positive management. With the potential for an increased number of false positives, particularly from intensive scans, the establishment of an efficient triage process is essential. This will ensure that false positives are quickly identified and disregarded, saving valuable time and resources.

In addition, it is beneficial to foster a strong culture of security awareness within your development team. Training developers to understand and address security issues identified by DAST scans reduces the security feedback loop and strengthens the application’s security posture. This symbiosis between automated scanning and human expertise is a cornerstone of an effective, balanced security strategy.

Summary

In making the decision between rapid and intensive scans, it’s important to recognize that it’s not a simple binary choice. Instead, it requires a thoughtful consideration of specific requirements and constraints. By adopting a stratified approach to DAST scanning, organizations can achieve an optimal balance between immediacy and thoroughness.

Leveraging rapid scans offers the advantage of swift identification of potential vulnerabilities, providing immediate insights into critical security issues. On the other hand, intensive scans delve deeper into the application, meticulously examining every nook and cranny to uncover even the most intricate vulnerabilities. The combination of these approaches enables organizations to build a comprehensive security framework.

By employing rapid scans for timely responsiveness and intensive scans for meticulous scrutiny, organizations can strike the right equilibrium between speed and depth. This approach ensures the establishment of a robust and comprehensive security posture, safeguarding web applications against a wide range of potential threats.

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