What Is a Vulnerability Scanner? How It Works and Why You Need One
Written by the Rafter Team
A vulnerability scanner is a tool that automatically inspects your code, dependencies, and infrastructure for known security weaknesses. It compares what you've built against databases of known vulnerabilities — like the National Vulnerability Database (NVD) — and flags anything that could be exploited. In 2024, Sonatype's State of the Software Supply Chain report found that 1 in 8 open-source downloads contained a known vulnerability, meaning the average project pulls in exploitable code without developers ever realizing it.
Without a scanner, these flaws sit in production until an attacker finds them first.
Start securing your code — free →
How Does a Vulnerability Scanner Work?
Vulnerability scanners use several detection methods to catch different types of flaws.
Static Application Security Testing (SAST) analyzes your source code without running it. It parses code paths, data flows, and patterns to find issues like SQL injection, cross-site scripting, and hardcoded credentials. SAST catches bugs early — before they ever reach a running environment.
Software Composition Analysis (SCA) checks your third-party dependencies against vulnerability databases. When a library you depend on gets a CVE published against it, SCA flags the exact package and version in your project.
Dynamic Application Security Testing (DAST) probes a running application from the outside, simulating real attack traffic to find runtime vulnerabilities like authentication bypasses and misconfigurations.
Most modern scanners combine these approaches. Rafter, for example, runs SAST and SCA scans on every pull request, catching vulnerabilities in both your code and your dependency tree before they merge.
Why Every Development Team Needs One
The cost of fixing a vulnerability in production is 6x higher than catching it during development, according to IBM's Cost of a Data Breach Report (2024). Vulnerability scanners shift that discovery left — into your IDE, your CI/CD pipeline, and your pull request workflow.
Three reasons teams adopt scanners:
- Speed. Manual code review cannot keep up with the volume of code modern teams ship — especially teams using AI code generation. A scanner checks every line in seconds.
- Coverage. Humans miss patterns. Scanners match against thousands of known vulnerability signatures and CVE entries simultaneously.
- Compliance. Standards like SOC 2, PCI DSS, and ISO 27001 require regular vulnerability assessments. Automated scanning satisfies this continuously rather than once per audit cycle.
If your team ships code without scanning, you're relying on attackers to find your bugs for you. That's an expensive QA strategy.
What Should You Look for in a Scanner?
Not all vulnerability scanners are equal. When evaluating tools, prioritize these capabilities:
- CI/CD integration — the scanner should run automatically on every commit or pull request, not require manual triggers
- Low false-positive rate — noisy scanners get ignored, which is worse than no scanner at all
- Actionable output — results should include the file, line number, severity, and a clear remediation path
- AI-generated code support — tools like Copilot and Cursor produce code that follows different vulnerability patterns than hand-written code
Related Resources
- Vulnerability Scanning Guide: Tools, Types, and How to Choose
- Automated Security Scanning: Set Up CI/CD Protection in 5 Minutes
- CI/CD Security Best Practices Every Developer Should Know
- Vulnerable and Outdated Components: OWASP Top 10
- AI Code Security in 2026: The Complete Resource Guide
- Securing AI-Generated Code: Best Practices