Static Malware Analysis Techniques

Introduction

Static malware analysis involves examining malicious software without executing it. This approach allows analysts to understand the malware's structure, functionality, and potential impact while maintaining a safe analysis environment.

Preparation and Safety

Analysis Environment

• Isolated Network: Completely isolated from production networks
• Virtual Machines: Disposable analysis environments
• Snapshots: Regular VM snapshots for quick recovery
• Air-Gapped Systems: Physical isolation for highly dangerous samples

Safety Protocols

• Never Execute: Static analysis means no execution
• Hash Verification: Verify sample integrity with cryptographic hashes
• Documentation: Maintain detailed analysis logs
• Chain of Custody: Proper evidence handling procedures

File Format Analysis

Portable Executable (PE) Analysis

• PE Headers: Examine DOS, NT, and optional headers
• Section Analysis: Code, data, and resource sections
• Import/Export Tables: API dependencies and exposed functions
• Digital Signatures: Certificate validation and trust chains

Other File Formats

• ELF Files: Linux executable analysis
• Mach-O: macOS binary examination
• Office Documents: Macro and embedded object analysis
• PDF Files: JavaScript and embedded content analysis

String Analysis

Extracting Strings

```bash

Basic string extraction

strings malware.exe > strings.txt

Unicode strings

strings -e l malware.exe > unicode_strings.txt

Minimum length filtering

strings -n 8 malware.exe > long_strings.txt
```

String Categories

• URLs and Domains: Network indicators
• File Paths: Target locations and dependencies
• Registry Keys: System modification indicators
• Error Messages: Functionality clues
• Encryption Keys: Cryptographic artifacts

Disassembly and Code Analysis

Disassemblers

• IDA Pro: Industry standard disassembler
• Ghidra: NSA's open-source reverse engineering tool
• Radare2: Command-line reverse engineering framework
• x64dbg: Windows debugging and disassembly

Assembly Analysis Techniques

• Control Flow: Function calls and program flow
• Data Flow: Variable usage and manipulation
• API Calls: System interaction points
• Obfuscation Detection: Packed or encrypted code identification

Cryptographic Analysis

Encryption Detection

• Entropy Analysis: High entropy indicates encryption/compression
• Cryptographic Constants: Known algorithm signatures
• Key Scheduling: Encryption key generation patterns
• Cipher Identification: Algorithm fingerprinting

Hash Analysis

```bash

File hashes

md5sum malware.exe
sha1sum malware.exe
sha256sum malware.exe

Import hash (ImpHash)

python imphash.py malware.exe

Fuzzy hashing

ssdeep malware.exe
```

Metadata Extraction

File Properties

• Compilation Timestamp: When the malware was built
• Compiler Information: Development environment details
• Version Information: Embedded version strings
• Digital Certificates: Code signing information

EXIF and Embedded Data

• Author Information: Creator metadata
• Creation Tools: Software used for creation
• Embedded Resources: Icons, strings, and data
• Hidden Streams: Alternate data streams (ADS)

Network Indicators

Static Network Analysis

• Hardcoded IPs: Command and control servers
• Domain Names: Communication endpoints
• URL Patterns: Web-based communication
• Protocol Analysis: Network communication methods

Configuration Extraction

• C2 Servers: Command and control infrastructure
• Encryption Keys: Communication encryption
• User Agents: HTTP header information
• Port Numbers: Network service ports

Behavioral Indicators

File System Operations

• File Creation: New files and locations
• File Modification: Target file changes
• Directory Operations: Folder creation and deletion
• Hidden Files: Concealment techniques

Registry Operations

• Persistence Mechanisms: Startup and service entries
• Configuration Storage: Settings and parameters
• System Modifications: Security and policy changes
• Forensic Artifacts: Analysis traces

Obfuscation and Packing

Packing Detection

```bash

Entropy calculation

python entropy.py malware.exe

Packer identification

peid malware.exe
detect-it-easy malware.exe

Section analysis

objdump -h malware.exe
```

Common Obfuscation Techniques

• String Encryption: Encrypted string literals
• Control Flow Obfuscation: Complex branching patterns
• Dead Code Insertion: Meaningless code additions
• API Hashing: Dynamic API resolution

Documentation and Reporting

Analysis Documentation

• Executive Summary: High-level findings
• Technical Details: Detailed analysis results
• Indicators of Compromise: IOCs for detection
• Mitigation Recommendations: Response actions

IOC Generation

```yaml

YARA Rule Example

rule Malware_Family_Detection {
meta:
description = "Detects specific malware family"
author = "Security Analyst"
date = "2024-01-30"

strings:
    $string1 = "unique_string_pattern"
    $string2 = { 48 89 E5 48 83 EC 20 }

condition:
    $string1 or $string2

}
```

Tools and Resources

Essential Tools

• Hex Editors: HxD, 010 Editor
• Disassemblers: IDA Pro, Ghidra, Radare2
• PE Analyzers: PEiD, CFF Explorer, PE-bear
• String Extractors: Strings, FLOSS
• Hash Calculators: HashCalc, md5deep

Online Resources

• VirusTotal: Multi-engine malware scanning
• Hybrid Analysis: Automated analysis platform
• Any.run: Interactive malware analysis
• Joe Sandbox: Comprehensive analysis reports

Best Practices

Analysis Workflow

1. Initial Triage: Basic file information and hashes
2. String Analysis: Extract and categorize strings
3. Structural Analysis: PE headers and sections
4. Disassembly: Code analysis and function identification
5. IOC Extraction: Generate detection signatures
6. Documentation: Comprehensive analysis report

Quality Assurance

• Peer Review: Second analyst verification
• Tool Validation: Cross-reference with multiple tools
• False Positive Testing: Validate IOCs against clean files
• Continuous Learning: Stay updated with new techniques

Conclusion

Static malware analysis is a critical skill for cybersecurity professionals. By systematically examining malware without execution, analysts can safely understand threats, generate detection signatures, and develop effective countermeasures while minimizing risk to analysis infrastructure.