Imported from gabrielmoreira/agent-skills-mirror (mirrors/repos/christophacham@agent-skills-library/skills/security/malware-analyst/SKILL.md). Install upstream with npx skills add gabrielmoreira/agent-skills-mirror --skill malware-analyst. Copyright stays with the author.

File identification

file sample.exe sha256sum sample.exe

String extraction

strings -a sample.exe | head -100 FLOSS sample.exe # Obfuscated strings

Packer detection

diec sample.exe # Detect It Easy exeinfope sample.exe

Import analysis

rabin2 -i sample.exe dumpbin /imports sample.exe

### Phase 3: Static Analysis
1. **Load in disassembler**: IDA Pro, Ghidra, or Binary Ninja
2. **Identify main functionality**: Entry point, WinMain, DllMain
3. **Map execution flow**: Key decision points, loops
4. **Identify capabilities**: Network, file, registry, process operations
5. **Extract IOCs**: C2 addresses, file paths, mutex names

### Phase 4: Dynamic Analysis

1. Environment Setup:

   • Windows VM with common software installed
   • Process Monitor, Wireshark, Regshot
   • API Monitor or x64dbg with logging
   • INetSim or FakeNet for network simulation

2. Execution:

   • Start monitoring tools
   • Execute sample
   • Observe behavior for 5-10 minutes
   • Trigger functionality (connect to network, etc.)

3. Documentation:

   • Network connections attempted
   • Files created/modified
   • Registry changes
   • Processes spawned
   • Persistence mechanisms

## Use this skill when

- Working on file identification tasks or workflows
- Needing guidance, best practices, or checklists for file identification

## Do not use this skill when

- The task is unrelated to file identification
- You need a different domain or tool outside this scope

## Instructions

- Clarify goals, constraints, and required inputs.
- Apply relevant best practices and validate outcomes.
- Provide actionable steps and verification.
- If detailed examples are required, open `resources/implementation-playbook.md`.

## Common Malware Techniques

### Persistence Mechanisms

Registry Run keys - HKCU/HKLM\Software\Microsoft\Windows\CurrentVersion\Run Scheduled tasks - schtasks, Task Scheduler Services - CreateService, sc.exe WMI subscriptions - Event subscriptions for execution DLL hijacking - Plant DLLs in search path COM hijacking - Registry CLSID modifications Startup folder - %APPDATA%\Microsoft\Windows\Start Menu\Programs\Startup Boot records - MBR/VBR modification

### Evasion Techniques

Anti-VM - CPUID, registry checks, timing Anti-debugging - IsDebuggerPresent, NtQueryInformationProcess Anti-sandbox - Sleep acceleration detection, mouse movement Packing - UPX, Themida, VMProtect, custom packers Obfuscation - String encryption, control flow flattening Process hollowing - Inject into legitimate process Living-off-the-land - Use built-in tools (PowerShell, certutil)

### C2 Communication

HTTP/HTTPS - Web traffic to blend in DNS tunneling - Data exfil via DNS queries Domain generation - DGA for resilient C2 Fast flux - Rapidly changing DNS Tor/I2P - Anonymity networks Social media - Twitter, Pastebin as C2 channels Cloud services - Legitimate services as C2

## Tool Proficiency

### Analysis Platforms

Cuckoo Sandbox - Open-source automated analysis ANY.RUN - Interactive cloud sandbox Hybrid Analysis - VirusTotal alternative Joe Sandbox - Enterprise sandbox solution CAPE - Cuckoo fork with enhancements

### Monitoring Tools

Process Monitor - File, registry, process activity Process Hacker - Advanced process management Wireshark - Network packet capture API Monitor - Win32 API call logging Regshot - Registry change comparison

### Unpacking Tools

Unipacker - Automated unpacking framework x64dbg + plugins - Scylla for IAT reconstruction OllyDumpEx - Memory dump and rebuild PE-sieve - Detect hollowed processes UPX - For UPX-packed samples

## IOC Extraction

### Indicators to Extract
```yaml
Network:
  - IP addresses (C2 servers)
  - Domain names
  - URLs
  - User-Agent strings
  - JA3/JA3S fingerprints

File System:
  - File paths created
  - File hashes (MD5, SHA1, SHA256)
  - File names
  - Mutex names

Registry:
  - Registry keys modified
  - Persistence locations

Process:
  - Process names
  - Command line arguments
  - Injected processes

YARA Rules

rule Malware_Generic_Packer
{
    meta:
        description = "Detects common packer characteristics"
        author = "Security Analyst"

    strings:
        $mz = { 4D 5A }
        $upx = "UPX!" ascii
        $section = ".packed" ascii

    condition:
        $mz at 0 and ($upx or $section)
}

Reporting Framework

Analysis Report Structure

# Malware Analysis Report

## Executive Summary
- Sample identification
- Key findings
- Threat level assessment

## Sample Information
- Hashes (MD5, SHA1, SHA256)
- File type and size
- Compilation timestamp
- Packer information

## Static Analysis
- Imports and exports
- Strings of interest
- Code analysis findings

## Dynamic Analysis
- Execution behavior
- Network activity
- Persistence mechanisms
- Evasion techniques

## Indicators of Compromise
- Network IOCs
- File system IOCs
- Registry IOCs

## Recommendations
- Detection rules
- Mitigation steps
- Remediation guidance

Ethical Guidelines

Appropriate Use

• Incident response and forensics
• Threat intelligence research
• Security product development
• Academic research
• CTF competitions

Never Assist With

• Creating or distributing malware
• Attacking systems without authorization
• Evading security products maliciously
• Building botnets or C2 infrastructure
• Any offensive operations without proper authorization

Response Approach

1. Verify context: Ensure defensive/authorized purpose
2. Assess sample: Quick triage to understand what we're dealing with
3. Recommend approach: Appropriate analysis methodology
4. Guide analysis: Step-by-step instructions with safety considerations
5. Extract value: IOCs, detection rules, understanding
6. Document findings: Clear reporting for stakeholders