Combining SAST and DAST
Why static and dynamic application security testing complement each other — different perspectives, different weaknesses, and combined coverage that neither technique achieves alone.
Primary question: Why should organizations use SAST and DAST together?
Direct answer
SAST and DAST observe an application from different perspectives; combining them provides visibility that neither technique achieves alone
SAST analyzes source code before the application runs and DAST analyzes a running application from the outside. Neither technique alone provides complete visibility — SAST cannot observe runtime behavior and DAST cannot observe code that is never exercised at runtime. Combining both techniques provides complementary coverage that is stronger than either technique alone. [derscanner-sast][derscanner-dast]
SAST finds weaknesses in code structure and logic. DAST finds weaknesses in how the running application behaves under attack. A finding that appears in both analyses has both code-level and runtime evidence. A finding that appears in only one analysis may still be important — it simply reflects the different perspectives each technique provides. [derscanner-sast][derscanner-dast]
Definitions
SAST (Static Application Security Testing)
Analysis of application source code, bytecode, or binaries without executing the application. SAST identifies code-level weaknesses such as input handling issues, insecure configurations, and vulnerable function calls.
DAST (Dynamic Application Security Testing)
Analysis of a running application by sending inputs and observing behavior. DAST identifies exploitable behavior at the application layer, including runtime configuration issues and authentication-related weaknesses.
Complementary testing
Using multiple analysis techniques that observe different properties of the same application, where each technique compensates for the blind spots of the others.
The engineering problem
Organizations that rely on only SAST miss runtime-configured weaknesses, authentication-related issues, and behavior that only appears when the application is running with real data and user interactions. [derscanner-dast]
Organizations that rely on only DAST miss code-level weaknesses in paths that are not exercised during testing, cannot identify the root cause of runtime issues from source code, and cannot observe the full codebase without deploying and exercising every code path. [derscanner-sast]
Using both SAST and DAST without correlation — simply running both and displaying results side by side — does not by itself provide the combined visibility that structured correlation can deliver. [derscanner-sast][derscanner-dast]
Security controls
Each control inspects a different artifact and produces evidence for an engineering decision.
Static analysis
SAST- Artifact
- Application source code, bytecode, or binaries.
- Risk
- Code-level security weaknesses that exist in the codebase regardless of runtime behavior.
- Output
- SAST findings that identify security weaknesses in source code, including code location, severity, and analysis context.
Evidence: DerScanner static analysis documentation
Dynamic analysis
DAST- Artifact
- Running application, including deployed endpoints, APIs, and user interfaces.
- Risk
- Runtime-configured weaknesses, authentication-related issues, and exploitable behavior that only manifests when the application is running.
- Output
- DAST findings that identify security weaknesses in the running application, including evidence of exploitable behavior.
Verification workflow
- SAST analyzes source code during development or build to identify code-level weaknesses.
- DAST analyzes the running application in a test or staging environment to identify runtime weaknesses.
- Findings from both analyses are reviewed together to understand the full security posture.
- Correlation between SAST and DAST findings provides additional context for prioritization.
- Remediation addresses findings from both analyses, with rescan to verify fixes.
DerScanner · Enterprise
Relationship to DerScanner
DerScanner provides SAST, DAST, and results-correlation capabilities that can be used together for complementary application security testing.
DerScanner performs static analysis of source code and reports detected security weaknesses. [derscanner-sast]
DerScanner performs dynamic analysis of running applications and reports detected security weaknesses. [derscanner-dast]
Limits of verification
- SAST cannot observe runtime behavior, runtime configuration, or authentication-related weaknesses.
- DAST cannot observe code that is never exercised during the scan, cannot identify the root cause from source code, and cannot analyze code that is not deployed.
- Combining SAST and DAST does not provide complete security coverage. Both techniques have inherent limitations.
- A finding present in only one analysis does not automatically mean the other technique would find it if run again.
Related knowledge
SAST/DAST Results Correlation
How correlation between SAST and DAST findings provides structured evidence beyond side-by-side results
Relationship: related-toCode-to-Runtime Security Testing
Connecting code-level weaknesses with runtime application behavior
Relationship: related-toWhen SAST and DAST Disagree
Why SAST and DAST may produce different results and how to interpret disagreements
Relationship: related-toMulti-Layer Application Security Testing
Code, dependencies, and running application as complementary testing layers
Relationship: related-toDerScanner
Product line providing SAST, DAST, and correlation capabilities
Relationship: related-toCanonical terms used: SAST; DAST; Complementary testing; Static analysis; Dynamic analysis.
Evidence and references
- DerScanner static analysis documentationDerScanner performs static analysis and reports source-code security findings, including vulnerable imports and function calls to dependencies.
derscanner-sast - DerScanner dynamic analysis documentationDerScanner performs dynamic analysis of running applications and reports detected security weaknesses, including runtime behavior and exploitable conditions.
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Combining SAST and DAST