Malware Analyst

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name: malware-analyst version: 1.0.0 description: "Expert malware analysis for defensive security research. Static and dynamic analysis, sandbox triage, IOC extraction, unpacking, and malware family identification. Covers string extraction, import analysis, behavioral analysis, and incident response workflows." metadata: model: opus

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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

yara 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

markdown

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

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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