CyberCode Academy

Course 33 - Static Analysis for Reverse Engineering | Episode 4: Static Analysis and Software Patching in x64dbg

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In this lesson, you’ll learn about: applying static analysis and patching to modify software behavior1. Core ConceptThis episode demonstrates how to use x64dbg with the xAnalyzer plugin to:
  • Analyze program logic without constant execution
  • Identify and modify key instructions
  • Alter how a program enforces trial limitations
2. Locating Critical Logic
  • Search for meaningful strings like:
    • "trial period remaining"
  • This helps you:
    • Jump directly to the function responsible for:
      • License checks
      • Expiration logic
3. Visualizing Program Flow
  • Use the graph view (CFG) to:
    • Understand decision paths clearly
  • Identify key instructions like:
    • JG (Jump if Greater)
👉 This instruction acts as:
  • A decision gate between:
    • Trial still valid
    • Trial expired
4. Understanding the Logic Behind the Trial
  • The program calculates remaining time using:
    • A fixed value (e.g., 1E in hex = 30 days)
  • It performs:
    • A subtraction between:
      • Current date
      • Allowed trial duration
5. The Patching Idea (High-Level)
  • Instead of changing logic flow, the approach modifies:
    • The data value controlling the limit
  • Example concept:
    • Increasing the maximum allowed duration
    • Results in a longer trial period
6. Validation Step
  • After modification:
    • Save the updated binary
    • Run the program
  • Confirm:
    • Trial duration has increased
    • Behavior matches expectations
Key Takeaways
  • Static analysis helps you pinpoint critical logic
  • CFG visualization simplifies complex branching decisions
  • Trial systems often rely on:
    • Simple arithmetic checks
  • Small changes in values can significantly affect behavior
  • Always verify changes through testing
Big PictureThis workflow shows how reverse engineers:
  • Break down program logic
  • Identify control points
  • Modify behavior with precision


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CyberCode AcademyBy CyberCode Academy