7 key types of application security testing

Static application security testing: Finding vulnerabilities at the source

Static application security testing (SAST) represents the foundation of modern application security testing. Often called white box testing, it analyzes source code, bytecode and binaries without executing the application. SAST tools examine code from the inside out, identifying potential security vulnerabilities during the earliest stages of development.

SAST tools parse application source code and apply a comprehensive set of security rules to detect common vulnerability patterns. These tools can identify problems such as SQL injection flaws, cross-site scripting (XSS) vulnerabilities, buffer overflows, hardcoded credentials and insecure cryptographic implementations -- all before a single line of code runs in production.

The primary strength of SAST lies in its ability to pinpoint exact locations where vulnerabilities exist, providing developers with file names, line numbers and detailed remediation guidance. This precision makes SAST invaluable during code reviews, enabling a team to address security flaws when they're least expensive to fix. Modern SAST tools integrate seamlessly into development environments and CI/CD pipelines, automatically scanning code commits and blocking builds that contain critical vulnerabilities.

SAST has its limitations, however. It can detect only vulnerabilities that exist in the application's own code, missing problems that might arise from how an environment is configured, third-party integrations or runtime behaviors. SAST tools also tend to generate false positives, particularly when analyzing complex code paths or dynamic code generation, requiring security teams to fine-tune rules and validate findings.

SAST proves most effective when implemented early in the development lifecycle, ideally integrated into developers' integrated development environments for real-time feedback and mandatory in build pipelines for comprehensive coverage.

Software composition analysis: Securing the supply chain

Software composition analysis (SCA) extends security testing beyond proprietary code to examine the open source and third-party components used in most modern applications.

While SAST focuses on code developers write, SCA analyzes code developers consume. This is a critical distinction, given that open source components account for 70-90% of most application codebases.

SCA tools create a comprehensive inventory of all dependencies, libraries and frameworks within an application. They then cross-reference this software bill of materials against vulnerability databases, such as the National Vulnerability Database. They identify known CVEs in dependencies, flag components with restrictive licenses and detect outdated libraries lacking security patches. Newer tools integrate directly into development workflows, scanning package managers, container images and infrastructure-as-code (IaC) templates while providing actionable remediation guidance.

SCA tools can create friction for development teams, however. They tend to be particularly noisy, generating hundreds or thousands of findings for applications with extensive dependency trees. Not all identified vulnerabilities represent actual risk; a critical flaw in a logging library's administrative interface might be irrelevant if that functionality isn't used or accessible in the developer's application. This creates a challenging prioritization problem, requiring security teams to distinguish between theoretical threats and practical ones.

Remediation can also prove complex. Updating dependencies might introduce breaking changes or incompatibilities. Fixes can also cascade into requiring updates across multiple interconnected components. Unlike SAST findings that point to specific code lines, SCA vulnerabilities often require architectural decisions about dependency management and upgrading strategies.

The field is rapidly evolving beyond basic vulnerability scanning toward comprehensive supply chain security. Modern approaches incorporate software provenance tracking, detecting malicious packages, monitoring for typosquatting attacks and implementing policy controls around dependency approval. These advances address not just known vulnerabilities, but also the broader risks of software supply chain compromises that have become increasingly prominent in recent high-profile attacks.

Dynamic application security testing: Testing applications in action

Dynamic application security testing (DAST) evaluates applications from the outside in, simulating how an attacker would interact with a running application. Often called black box testing, DAST tools crawl and probe web applications during runtime, identifying vulnerabilities that manifest only when code executes in its intended environment.

DAST works by systematically exploring web applications as if it were an automated penetration tester. It follows links, submits forms and attempts various attack payloads against input fields, parameters and endpoints. These tools excel at detecting runtime vulnerabilities such as authentication bypasses, session management flaws, server misconfigurations and injection attacks that depend on how the application processes user input in its actual deployment environment.

DAST's primary strength lies in its ability to find vulnerabilities that static analysis cannot detect. These include problems that arise from an environment's configuration, server settings, third-party integrations and complex runtime behaviors. DAST provides a realistic assessment of security posture from an attacker's perspective, testing applications exactly as they would be accessed in production. Modern DAST tools can authenticate into applications, maintain session state and handle complex single-page applications with JavaScript-heavy interfaces.

DAST complements rather than replaces other testing methods. It can test only what it can reach and discover through crawling -- potentially missing functionality behind authentication barriers or complex navigation paths. DAST tools struggle with applications that require specific input sequences or with business logic flows, and they cannot examine code paths that aren't triggered during testing. For large applications, DAST scanning can be slow, and testing might affect application performance.

DAST proves most valuable when integrated into staging environments that closely mirror production configurations, ideally running as part of predeployment validation processes. Some organizations also implement DAST in production environments during maintenance windows to catch configuration drift and deployment-specific vulnerabilities that surface only in live systems.

API security testing: Extending DAST

As applications increasingly adopt API-first architectures and microservices designs, traditional web-focused DAST tools often fall short when testing REST, GraphQL and SOAP APIs that lack conventional web interfaces. API security testing extends DAST principles specifically for these programmatic interfaces, using API specifications, such as OpenAPI/Swagger and GraphQL schemas, and traffic analysis to understand and test API endpoints systematically.

API-focused testing tools excel at detecting authorization flaws, parameter tampering, injection attacks targeting API endpoints and business logic vulnerabilities unique to API workflows. They can test complex authentication mechanisms, such as OAuth flows; validate rate limiting and input validation controls; and identify sensitive data exposure in API responses. Unlike traditional DAST crawling, API testing can directly target specific endpoints with crafted payloads and test edge cases that might not be discoverable through conventional web navigation.

API testing requires more upfront configuration than traditional DAST. Tools need API documentation or traffic samples to understand available endpoints and expected parameters. This dependency on specifications means poorly documented APIs might receive incomplete coverage. Testing effectiveness relies heavily on the accuracy and completeness of available API schemas.

Interactive application security testing: Best of both worlds

Interactive application security testing (IAST) combines the strengths of SAST and DAST by embedding security sensors directly within running applications. Unlike DAST's external probing or SAST's static analysis, IAST monitors security-relevant events in real time as the application executes.

IAST tools work by deploying lightweight agents or libraries that observe application behavior from the inside during functional testing, QA processes or even production traffic. These sensors track data flow from sources (user inputs) to sinks (databases, file systems), identifying when untrusted data reaches sensitive operations without proper validation or sanitization. This approach dramatically reduces false positives, since IAST tools report only the vulnerabilities along code paths that execute.

The key advantage of IAST is accuracy. It provides SAST's precise code location details with DAST's runtime context, eliminating many false positives that plague other testing methods. IAST can detect complex vulnerabilities involving multiple application layers and provide rich contextual information about exploitability conditions.

IAST requires application instrumentation, however, which can introduce performance overhead and deployment complexity. It also depends on comprehensive test coverage to trigger vulnerable code paths. This means untested functionality remains unanalyzed, making IAST effectiveness directly tied to the quality of functional testing processes.

Container security scanning: Securing the deployment pipeline

Container security scanning addresses vulnerabilities in Docker images, configurations and runtime environments that traditional application testing tools miss. Container scanning tools inspect base OS images for CVEs, examine container configurations for misconfigurations and validate security settings, such as proper user privileges and resource constraints.

Container scanners integrate into CI/CD pipelines. They block vulnerable images before deployment and monitor running containers for drift. They excel at detecting inherited vulnerabilities from base images, overprivileged containers, exposed secrets and misconfigurations that could enable container-escape attacks.

Container scanning can be noisy when analyzing large image repositories, however, and remediation often requires coordinating base image updates across multiple teams. The layered nature of containers makes vulnerability attribution complex, while runtime monitoring must balance security visibility with performance impact. Container security works best when implemented throughout the entire lifecycle, from build-time scanning to runtime policy enforcement in orchestration platforms.

Infrastructure as code security: Preventing cloud misconfigurations

IaC security scanning tools analyze Terraform, AWS CloudFormation, Kubernetes YAML and other infrastructure templates for security misconfigurations before they reach production environments. As organizations increasingly define their cloud infrastructure through code, these tools have become critical for preventing the misconfigurations that cause most cloud security breaches.

IaC scanners examine template files for dangerous settings, such as overly permissive access controls, unencrypted storage, exposed databases and insecure network configurations. They integrate into development workflows to catch issues during code reviews and block deployments that violate security policies, preventing misconfigurations from reaching live environments.

These tools excel at detecting common cloud security failures, such as publicly accessible S3 buckets, overprivileged IAM roles, unencrypted databases and missing security groups. Modern scanners provide policy-as-code capabilities, enabling organizations to codify their security requirements and automatically enforce compliance across all infrastructure deployments.

IaC scanning's effectiveness depends heavily on comprehensive template coverage and accurate policy definitions. Tools can struggle with complex conditional logic or dynamic resource creation, and maintaining current policies across rapidly evolving cloud services requires ongoing attention. IaC security proves most valuable when integrated early in infrastructure development workflows, ideally with automated policy enforcement that prevents risky configurations from reaching production.

Application security needs a multipronged approach

No single application security testing tool can catch every vulnerability. Effective application security requires a layered approach that combines multiple testing methods: SAST for early code analysis, DAST for runtime validation, SCA for dependency risks and specialized tools for containers and infrastructure.

The key to success lies in strategic integration. Embed these tools into development workflows where they provide maximum value with minimal friction. By implementing security testing throughout the development lifecycle rather than as a final gate, organizations can maintain development velocity while building genuinely secure applications.

Colin Domoney is a software security consultant who evangelizes DevSecOps and helps developers secure their software. He previously worked for Veracode and 42Crunch and authored a book on API security. He is currently a CTO and co-founder, and an independent security consultant.