Reverse Engineering Malware with Ghidra

When to Use

• Static and dynamic analysis have identified suspicious functionality that requires deeper code-level understanding
• You need to reverse engineer C2 communication protocols, encryption algorithms, or custom obfuscation
• Understanding the exact exploit mechanism or vulnerability targeted by a malware sample
• Extracting hardcoded configuration data (C2 addresses, encryption keys, campaign IDs) embedded in compiled code
• Developing precise YARA rules or detection signatures based on unique code patterns

Do not use for initial triage of unknown samples; perform static analysis with PEStudio and behavioral analysis with Cuckoo first.

Prerequisites

• Ghidra 11.x installed (download from https://ghidra-sre.org/) with JDK 17+
• Analysis VM isolated from production network (Windows or Linux host)
• Familiarity with x86/x64 assembly language and Windows API conventions
• PDB symbol files for Windows system DLLs to improve decompilation accuracy
• Ghidra scripts repository (ghidra_scripts) for automated analysis tasks
• Secondary reference: IDA Free or Binary Ninja for cross-validation of analysis results

Workflow

Step 1: Create Project and Import Binary

Set up a Ghidra project and import the malware sample:

1. Launch Ghidra: ghidraRun (Linux) or ghidraRun.bat (Windows)
2. File -> New Project -> Non-Shared Project -> Select directory
3. File -> Import File -> Select malware binary
4. Ghidra auto-detects format (PE, ELF, Mach-O) and architecture
5. Accept default import options (or specify base address if known)
6. Double-click imported file to open in CodeBrowser
7. When prompted, run Auto Analysis with default analyzers enabled

Headless analysis for automation:

# Run Ghidra headless analysis with decompiler
/opt/ghidra/support/analyzeHeadless /tmp/ghidra_project MalwareProject \
  -import suspect.exe \
  -postScript ExportDecompilation.py \
  -scriptPath /opt/ghidra/scripts/ \
  -deleteProject

Step 2: Identify Key Functions and Entry Points

Navigate the binary to locate critical code sections:

Navigation Strategy:
━━━━━━━━━━━━━━━━━━━
1. Start at entry point (OEP) - follow execution from _start/WinMain
2. Check Symbol Tree for imported functions (Window -> Symbol Tree)
3. Search for cross-references to suspicious APIs:
   - VirtualAlloc/VirtualAllocEx (memory allocation for injection)
   - CreateRemoteThread (remote thread injection)
   - CryptEncrypt/CryptDecrypt (encryption operations)
   - InternetOpen/HttpSendRequest (C2 communication)
   - RegSetValueEx (persistence via registry)
4. Use Search -> For Strings to find embedded URLs, IPs, and paths
5. Check the Functions window sorted by size (large functions often contain core logic)

Ghidra keyboard shortcuts for efficient navigation:

G         - Go to address
Ctrl+E    - Search for strings
X         - Show cross-references to current location
Ctrl+Shift+F - Search memory for byte patterns
L         - Rename label/function
;         - Add comment
T         - Retype variable
Ctrl+L    - Retype return value

Step 3: Analyze Decompiled Code

Use Ghidra's decompiler to understand function logic:

// Example: Ghidra decompiler output for a decryption routine
// Analyst renames variables and adds types for clarity

void decrypt_config(BYTE *encrypted_data, int data_len, BYTE *key, int key_len) {
    // XOR decryption with rolling key
    for (int i = 0; i < data_len; i++) {
        encrypted_data[i] = encrypted_data[i] ^ key[i % key_len];
    }
    return;
}

// Analyst actions in Ghidra:
// 1. Right-click parameters -> Retype to correct types (BYTE*, int)
// 2. Right-click variables -> Rename to meaningful names
// 3. Add comments explaining the algorithm
// 4. Set function signature to propagate types to callers

Step 4: Trace C2 Communication Logic

Follow the network communication code path:

Analysis Steps for C2 Protocol Reverse Engineering:
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
1. Find InternetOpenA/WinHttpOpen call -> trace to wrapper function
2. Follow data flow from encrypted config -> URL construction
3. Identify HTTP method (GET/POST), headers, and body format
4. Locate response parsing logic (JSON parsing, custom binary protocol)
5. Map the C2 command dispatcher (switch/case or jump table)
6. Document the command set (download, execute, exfiltrate, update, uninstall)

…