Four Pillars of Security Testing
Application security testing falls into four distinct methodologies, each targeting vulnerabilities from a different angle:
Static Application Security Testing (SAST) analyzes source code, bytecode, or binaries without executing the application. It examines code structure, data flow, and control flow to identify vulnerabilities such as injection flaws, hardcoded secrets, and insecure configurations at the earliest possible stage.
Dynamic Application Security Testing (DAST) tests running applications from the outside by sending crafted HTTP requests and analyzing responses. DAST simulates attacker behavior, probing for vulnerabilities like XSS, authentication flaws, and server misconfigurations that only manifest at runtime.
Software Composition Analysis (SCA) inventories third-party dependencies—open-source libraries, frameworks, and transitive packages—and cross-references them against vulnerability databases like the National Vulnerability Database (NVD) and OSV.dev. SCA also checks license compliance and identifies end-of-life components.
Interactive Application Security Testing (IAST) combines elements of SAST and DAST by instrumenting the application at runtime. An IAST agent monitors code execution during normal testing or QA, tracking how data flows through the application to identify real vulnerabilities with lower false-positive rates than SAST or DAST alone.
How Each Approach Works
SAST: White-Box Analysis
SAST tools parse source code into abstract syntax trees (ASTs) and analyze data flow paths from sources (user input) to sinks (dangerous functions). Because SAST sees the full codebase, it can trace vulnerabilities across function calls and modules. Results include the exact file, line number, and CWE classification. SAST runs without deploying the application, making it ideal for CI/CD integration.
DAST: Black-Box Testing
DAST tools crawl the application, discover endpoints, and send malicious payloads—SQL injection strings, XSS vectors, fuzzing inputs. They analyze HTTP responses for error messages, timing differences, and behavioral changes that indicate a vulnerability. DAST requires a running environment and cannot pinpoint the vulnerable line of code.
SCA: Dependency Intelligence
SCA tools parse manifest files (package.json, requirements.txt, pom.xml, go.mod) and lockfiles to build a complete dependency tree, including transitive dependencies. Each package version is matched against CVE databases. SCA also detects known malicious packages that have been published to registries with typosquatting or supply chain attacks.
IAST: Instrumented Runtime
IAST agents are deployed alongside the application (often as middleware or JVM agents). As QA tests exercise the application, the agent traces request data through the code. When user input reaches a vulnerable function without sanitization, IAST reports the exact data flow path with minimal false positives.
When to Use Each Approach
No single testing method catches everything. Each approach has strengths that compensate for the others' blind spots:
- SAST: Use in development and CI/CD. Catches injection flaws, hardcoded secrets, and insecure patterns before code is deployed. Fast feedback loop—results in seconds.
- DAST: Use in staging and pre-production. Catches runtime issues like misconfigured headers, authentication flaws, and server-side errors that SAST cannot see.
- SCA: Use continuously. Dependency vulnerabilities are disclosed daily. SCA must run on every build and on a schedule to catch newly published CVEs in existing dependencies.
- IAST: Use during QA and integration testing. Best for reducing false positives from SAST by confirming which code paths are actually reachable with real data.
The combination of SAST + SCA in CI/CD with DAST in staging provides the broadest coverage for most teams. IAST adds precision when false-positive volume from SAST becomes a burden.
Where CodeSlick Fits (SAST + SCA)
CodeSlick combines SAST and SCA in a single tool that runs across JavaScript, TypeScript, Python, Java, and Go. The SAST engine performs 294 security checks covering OWASP 2025 at 95%, with CWE and CVSS classification on every finding. The SCA engine scans dependency manifests and detects known malicious packages through OSV.dev integration.
- Web scanner: Paste code at
codeslick.dev/analyzefor instant results—no account required - GitHub App: Automated PR reviews with inline comments on vulnerable lines and SARIF upload to the GitHub Security tab
- CLI: Pre-commit hooks and CI/CD integration with pass/fail exit codes
Analysis completes in under 3 seconds with AI-powered fix suggestions for every finding.
Run SAST and SCA on your code in under 3 seconds with no signup required.