DAST vs SAST: 5 Key Differences, Pros/Cons and How to Choose

DAST vs. SAST: The Key Differences

SAST and DAST serve different purposes within the software development lifecycle. Here are the key differences:

1. Testing Approach

SAST, a white-box testing method, analyzes the application’s source code, bytecode, or binaries without executing the program. This allows SAST to scrutinize every line of code, making it highly effective for identifying security flaws that could be introduced through poor coding practices. SAST tools integrate into the development pipeline, providing developers with detailed feedback on code weaknesses as they work.

DAST, as a black-box testing method, evaluates the application from an external perspective while it is running. It simulates attack patterns to assess the security of a deployed application’s functionality, interfaces, and responses to malicious input. DAST’s dynamic approach makes it ideal for testing runtime vulnerabilities and ensuring that security defenses behave as expected under real-world conditions. Together, SAST and DAST provide a complete view of an application’s security, covering both code-level weaknesses and runtime vulnerabilities.

2. Visibility and Scope

SAST provides a complete view of the application’s codebase, allowing thorough analysis of all components. Its in-depth inspection identifies potential flaws at the code level. However, it cannot ascertain the security of runtime processes or interactions with external components.

DAST, by contrast, has a limited view of the internals but excels at evaluating interface and runtime security. It tests the application’s defensive mechanisms as an attacker would, providing insights into how the application is perceived externally. Its approach helps identify misconfigurations and vulnerabilities exposed only during operation, offering a focused view on runtime and post-deployment security aspects.

3. Relevancy to SDLC Stages

SAST and DAST operate at different stages of the software development lifecycle (SDLC), making them suitable for distinct phases of security testing.

SAST is typically employed during the early stages of development, such as coding and build phases. By analyzing the source code before the application is executed, SAST enables developers to identify and fix vulnerabilities early, reducing the cost and effort associated with late-stage defect remediation. It integrates well into CI/CD pipelines, providing continuous feedback on code security as part of the development workflow.

DAST is applied later in the SDLC, usually during the testing or staging phases, and can extend into production monitoring. Because it evaluates applications in their running state, DAST is best suited for testing fully or partially functional applications. This approach ensures that runtime vulnerabilities, configuration errors, and operational flaws are identified before the application is deployed or while it is in use.

4. Types of Vulnerabilities Detected

SAST is effective at detecting vulnerabilities like authentication flaws, code injection vulnerabilities, buffer overflows, and other issues identifiable without running the application. It checks for conditions that could lead to security weaknesses by examining the code, providing extensive lists of potential vulnerabilities that developers can fix early on.

DAST identifies weaknesses appearing during application execution, such as input validation issues, session handling problems, and misconfigurations seen only in dynamic contexts. It's capable of finding flaws like broken authentication and cross-site scripting, providing insights into vulnerabilities that affect the application as users interact with it, offering a complementary layer of security verification.

5. False Positives

SAST often generates more false positives due to its exhaustive analysis of code, where non-issues might be flagged as vulnerabilities. This can lead to the need for extensive review processes to differentiate actual security threats from benign code anomalies.

DAST may report fewer false positives, because it can validate the existence of vulnerabilities ina live environment. However, it can still misidentify benign application behaviors as vulnerabilities. This happens because DAST observes only the application output and interactions.

In both solutions, effective filtering and analysis are required to ensure accurate security assessments without unnecessary remediation efforts. Advanced solutions use AI to perform more nuanced analysis of vulnerabilities and reduce false positives.

Pros and Cons of SAST

Advantages:

• Early detection of vulnerabilities: SAST tools allow developers to identify security flaws early in the development lifecycle, reducing the cost and complexity of fixing issues before they reach production.
• Comprehensive code analysis: By examining the full codebase, SAST provides a deep analysis, identifying potential weaknesses in logic, data flow, and code structure.
• Developer-friendly integration: SAST tools can be integrated into IDEs and CI/CD pipelines, enabling automated security checks with every code change. This continuous feedback helps developers address issues quickly, fostering secure coding practices.

Limitations:

• High rate of false positives: Due to its exhaustive nature, SAST often flags benign issues as vulnerabilities, leading to “noise” in the results. Developers may need to spend extra time reviewing and validating each finding.
• Limited runtime context: SAST cannot evaluate issues that only emerge when the application is running, such as those arising from system configurations, external integrations, or dynamic interactions.
• Inability to simulate real-world attacks: Because it works on static code, SAST does not provide insights into how the application behaves under actual attack scenarios, leaving runtime vulnerabilities undetected.

Pros and Cons of DAST

Advantages:

• Realistic attack simulation: DAST tests the application in its live, running state, providing a realistic view of its security posture by simulating common attack scenarios. This approach helps uncover vulnerabilities that only appear at runtime.
• No source code access required: DAST does not require access to the application’s source code, making it suitable for testing third-party applications or systems with restricted code access.
• Focus on runtime security: By examining how the application responds to various inputs and interactions, DAST can detect vulnerabilities related to session management, authentication, and input validation, which are difficult to detect with static analysis.

Limitations:

• Limited coverage of codebase: Since DAST operates without visibility into the internal code structure, it may miss security flaws that are only detectable in the code itself, such as insecure coding patterns or unvalidated functions.
• Late in development lifecycle: DAST is generally performed later in the development process, meaning that identified vulnerabilities may require more time and resources to fix as compared to issues caught in earlier stages.
• Potential for false negatives: Some vulnerabilities may go undetected in DAST testing if specific attack scenarios are not part of the test or if the application hides vulnerabilities well during dynamic tests.

Combining SAST and DAST for Comprehensive Security

To achieve thorough application security, organizations often combine SAST and DAST. By integrating both types of testing, teams can address vulnerabilities at all stages of the software development lifecycle, covering both code-level issues and runtime security gaps.

Using SAST early in development allows teams to detect and resolve vulnerabilities before deployment. Since SAST scans code for logical flaws and poor coding practices, it helps establish a secure codebase from the start. With continuous integration in development environments, SAST enables frequent checks, allowing developers to catch and fix issues as they code.

DAST, performed later in the lifecycle, offers a critical layer of validation. By running tests on the live application, DAST detects vulnerabilities that only appear during execution, such as issues in authentication, session management, or data handling. This external perspective simulates actual attack conditions, providing insights into how the application withstands real-world threats.

Automated Penetration Testing with CyCognito

CyCognito built its external attack surface management (EASM) and security testing platform to replicate an attacker’s thought processes and workflows.

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With CyCognito your offensive security teams can pivot faster to human-led exploitation-based tests:

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• Learn more about CyCognito for automated security testing