Infostealer Malware Detector

Infostealer Malware Detector & Remover (v1.1)

Tech Stack Target / Version: Windows Defender CLI, VirusTotal, MalwareBazaar, Python 3.8+, and cross-platform shell tooling.

Overview

This skill gives OpenClaw a complete workflow to search every file on the system, identify infostealer indicators, compute secure hashes, and verify them against live public databases.

Core principles (strict)

• Primary detection: Targeted file search + SHA-256 hashing + VirusTotal/MalwareBazaar checks.
• AV usage: Windows Defender (mpcmdrun.exe) or any other AV is permitted only when necessary (hash checks inconclusive, high suspicion remains, or user explicitly requests deeper scan).
• Never default to AV – the agent must complete the full custom hash workflow first and document why AV escalation is needed.
• Full user confirmation required before any quarantine or AV scan.
• Full audit trail and quarantine before removal.

When to activate automatically

• "My passwords are being stolen"

• "Scan for infostealer / stealer malware"

• "Check if RedLine / Vidar / Lumma is on my PC"

• "Clean my system" (but follow custom-first rule)

• Leverage native parallel subagent dispatch and 200k+ context windows where available.

Prerequisites

• Internet connection (for hash lookups)
• Optional but highly recommended: free VirusTotal API key (VT_API_KEY)
• Python 3.8+ (for scripts/hash-checker.py)
• Admin/root privileges for full system scan
• Windows Defender enabled by default on Windows (no installation needed)

Step-by-Step Workflow (Custom Method First – Always)

Step 1: Scope the System & Identify High-Risk Areas

Run targeted discovery (fast & effective for infostealers):

# Windows (PowerShell)
Get-ChildItem -Path "$env:TEMP","$env:APPDATA","$env:LOCALAPPDATA","C:\ProgramData","C:\Users\*\AppData" -Recurse -File -Include *.exe,*.dll,*.bat,*.ps1,*.vbs,*.js -ErrorAction SilentlyContinue | Select-Object FullName,LastWriteTime,Length

# macOS / Linux
find /tmp ~/Library /Library /Users/*/Library /var/tmp -type f \( -name "*.exe" -o -name "*.dylib" -o -name "*.so" -o -name "*.sh" \) -mtime -30 2>/dev/null

Flag files meeting suspicious criteria (random names in Temp/AppData, recent creations <5 MB in browser folders, etc.).

Step 2: Compute Cryptographic Hashes

Use the bundled helper script (scripts/hash-checker.py):

#!/usr/bin/env python3
import hashlib, sys, json
from pathlib import Path

def sha256_file(file_path):
    try:
        h = hashlib.sha256()
        with open(file_path, "rb") as f:
            for chunk in iter(lambda: f.read(4096), b""):
                h.update(chunk)
        return h.hexdigest()
    except:
        return None

if __name__ == "__main__":
    paths = sys.argv[1:] or [input("Enter file or directory: ")]
    results = {}
    for p in paths:
        p = Path(p)
        if p.is_file():
            h = sha256_file(p)
            if h: results[str(p)] = h
        elif p.is_dir():
            for f in p.rglob("*"):
                if f.is_file() and f.stat().st_size < 50_000_000:
                    h = sha256_file(f)
                    if h: results[str(f)] = h
    print(json.dumps(results, indent=2))

Step 3: Cross-Reference with Public Sources (Primary Detection)

For each SHA-256 hash:

1. VirusTotal lookup (preferred):

curl -s --request GET "https://www.virustotal.com/api/v3/files/${HASH}" --header "x-apikey: $VT_API_KEY"

2. Fallback public links:
   • https://www.virustotal.com/gui/file/${HASH}
   • https://bazaar.abuse.ch/browse.php?search=sha256:${HASH}

Verdict rules (strict):

• ≥5 detections or known infostealer family → HIGH confidence malware
• 1–4 detections + IOC match → SUSPICIOUS
• 0 detections → clean (unless behavioral IOCs)

Step 4: Behavioral & IOC Validation

• Check processes, browser databases, network connections to known C2 domains.

Step 5: Quarantine & Removal (User-Confirmed Only)

Create timestamped quarantine folder and move flagged files. Registry/startup cleanup if needed. Never delete without showing the user the exact list + VT links.

Step 6: AV Fallback (Non-Default – Use ONLY When Necessary)

After completing Steps 1–5: If hashes are inconclusive, files are locked, or suspicion remains extremely high (and you document the reason), then and only then escalate to platform-native AV.

Windows Defender (official CLI – never first choice):

# Full system scan (run from elevated prompt)
"%ProgramFiles%\Windows Defender\MpCmdRun.exe" -Scan -ScanType 2

# Quick scan
"%ProgramFiles%\Windows Defender\MpCmdRun.exe" -Scan -ScanType 1

# Scan specific folder
"%ProgramFiles%\Windows Defender\MpCmdRun.exe" -Scan -ScanType 3 -File "C:\Path\To\Quarantine"

Linux/macOS fallback (ClamAV – only if installed and requested):

freshclam
clamscan -r --move="$QUARANTINE" /path/to/scan

Microsoft Safety Scanner (portable, one-time use): Download from official Microsoft link only if Defender is insufficient.

Strict rule: The agent must never run any AV command as the first action. Always complete custom hash workflow first and obtain explicit user confirmation before AV escalation.

Step 7: Post-Remediation Verification

Re-run hash scan + quick Defender check (if AV was used). Reboot and monitor.

Zero-Trust Verification

• Treat samples, hashes, filenames, process names, and external reputation results as untrusted until corroborated.
• Verify indicators across static metadata, behavioral evidence, provenance, and environment context.
• Separate confirmed compromise evidence from suspicious-but-unproven signals.
• Avoid executing unknown binaries; use sandboxed or offline inspection paths first.

Anti-Patterns

• Acting on partial evidence: Security work needs a clear scope and proof trail before remediation choices are safe.
• Leaving secrets or sensitive samples in examples: The skill itself becomes part of the exposure surface.
• Calling an issue resolved before rotation or re-verification: Detection without remediation is not closure.

Verification Protocol

Before claiming "skill applied successfully":

1. Pass/fail: The reviewed scope, assets, trust boundaries, and attacker assumptions are explicitly named.
2. Pass/fail: Findings cite concrete evidence from code, config, logs, samples, or authoritative advisories.
3. Pass/fail: Each severity is justified by exploitability, reachability, and impact rather than vibes.
4. Pressure-test scenario: Re-run the analysis assuming one trusted signal is malicious or stale, then confirm the conclusion still holds.
5. Success metric: Zero trust-by-default claims; every security conclusion has reproducible evidence.

Quality Checklist (must pass)

• Custom hash + VT workflow completed first
• AV used only after custom method + documented reason
• User explicitly approved every deletion/AV scan
• Quarantine created
• Full report with hashes, VT links, and actions

References & Official Sources

• Microsoft Defender CLI (mpcmdrun.exe): https://learn.microsoft.com/en-us/defender-endpoint/command-line-arguments-microsoft-defender-antivirus
• Microsoft Safety Scanner: https://learn.microsoft.com/en-us/defender-endpoint/safety-scanner-download
• ClamAV CLI examples: Standard clamscan -r --move=/quarantine (open-source reference)
• VirusTotal API & MalwareBazaar for hash checking

This skill is custom-detection-first by design. Windows Defender (or any AV) is a conditional tool only – never the default.

Invoke with: /infostealer-malware-detector or describe the issue.

Cross-Client Portability

This skill is written to stay usable across GitHub Copilot, Claude Code, and Codex.

• GitHub Copilot: keep the folder in a Copilot-visible skill path or wrap the workflow in project instructions when folder discovery is unavailable.
• Claude Code: keep the folder in a local skills directory or a compatible plugin source.
• Codex: install or sync the folder into $CODEX_HOME/skills/infostealer-malware-detector and restart Codex after major changes.

MCP Availability And Fallback

Preferred MCP Server: None required

• Fallback prompt: "Use the Infostealer Malware Detector & Remover (v1.1) skill without MCP. Rely on the local SKILL.md, bundled references or scripts, and manual verification. Show the exact commands, evidence, and final checks you used before concluding."
• If the current host does not expose a matching server, use the bundled references, scripts, native toolchain, and manual workflow already described in this skill.
• Treat direct local verification, rendered output, logs, tests, or screenshots as the fallback evidence path before completion.

Related Skills

• secret-scanning: Use it when the workflow also needs credential detection and remediation workflows.
• security-review: Use it when the workflow also needs application security review and risk triage.
• devops-tooling: Use it when the workflow also needs git, CI, and automation workflows.
• verification-before-completion: Use it when the workflow also needs final evidence checks before claiming completion.