Code Review for Security

Code review is one of the most effective ways to catch security vulnerabilities before they reach production. While automated tools like SAST scanners catch many issues, human reviewers excel at finding logic flaws, business rule violations, and context-dependent vulnerabilities that tools miss.

Security-focused code review requires a different mindset than functional review. Instead of asking "does this work?", you ask "how could this be abused?" This adversarial thinking helps identify vulnerabilities that developers might overlook.

This guide covers the essential skills for effective security code review:

• Security review mindset - Thinking like an attacker
• Common vulnerability patterns - What to look for in different languages
• Review checklists - Systematic approaches for thorough coverage
• Effective feedback - How to communicate security issues constructively

What You'll Learn

This guide consists of the following parts:

1. Security Review Fundamentals - Mindset, approach, and what tools miss
2. Vulnerability Patterns - Common issues by category (injection, auth, crypto, etc.)
3. Language-Specific Concerns - Python, JavaScript, Go, and Java patterns
4. Review Process and Feedback - Checklists, prioritization, and communication

Why Human Review Matters

Automated tools are essential but insufficient. Consider what they miss:

Issue Type	SAST Tools	Human Reviewers
SQL Injection (obvious)	Detects well	Detects well
Business logic flaws	Usually misses	Can identify
Insecure design patterns	Limited detection	Can identify
Authorization bypass	Often misses	Can identify
Race conditions	Rarely detects	Can identify
Cryptographic misuse	Partial detection	Can identify

Research shows that code review catches a significant percentage of security issues that automated tools miss - some studies estimate 50-70%. The combination of both approaches provides the strongest defense.

The Security Reviewer's Mindset

Effective security review requires shifting your perspective:

Developer Mindset          Security Reviewer Mindset
------------------         -------------------------
"How do I make this work?" "How could this be abused?"
"Happy path first"         "Edge cases and errors first"
"Trust user input"         "All input is malicious"
"This is internal only"    "Assume network is compromised"
"Users will behave"        "Assume malicious users"

This shift doesn't mean being paranoid about everything - it means systematically considering how each piece of code could be exploited.