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Three SKILL.md files had tags that were simply words split from the skill name (e.g., "analyzing", "block", "with", "logs") rather than meaningful discovery keywords. Replace with domain-specific terms that agents and search tools can actually use for routing. - analyzing-powershell-script-block-logging: [powershell, script-block-logging, event-id-4104, obfuscation-detection, windows-forensics, endpoint-security] - analyzing-azure-activity-logs-for-threats: [azure, cloud-security, azure-monitor, kql, threat-hunting, activity-logs] - analyzing-memory-forensics-with-lime-and-volatility: [memory-forensics, linux-forensics, lime, volatility, incident-response, kernel-modules] Co-Authored-By: Claude Code <noreply@anthropic.com>
71 lines
2.5 KiB
Markdown
71 lines
2.5 KiB
Markdown
---
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name: analyzing-powershell-script-block-logging
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description: Parse Windows PowerShell Script Block Logs (Event ID 4104) from EVTX files to detect obfuscated commands, encoded
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payloads, and living-off-the-land techniques. Uses python-evtx to extract and reconstruct multi-block scripts, applies entropy
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analysis and pattern matching for Base64-encoded commands, Invoke-Expression abuse, download cradles, and AMSI bypass attempts.
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domain: cybersecurity
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subdomain: security-operations
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tags:
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- powershell
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- script-block-logging
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- event-id-4104
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- obfuscation-detection
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- windows-forensics
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- endpoint-security
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version: '1.0'
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author: mahipal
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license: Apache-2.0
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nist_csf:
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- DE.CM-01
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- RS.MA-01
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- GV.OV-01
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- DE.AE-02
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---
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# Analyzing PowerShell Script Block Logging
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## When to Use
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- When investigating security incidents that require analyzing powershell script block logging
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- When building detection rules or threat hunting queries for this domain
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- When SOC analysts need structured procedures for this analysis type
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- When validating security monitoring coverage for related attack techniques
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## Prerequisites
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- Familiarity with security operations concepts and tools
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- Access to a test or lab environment for safe execution
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- Python 3.8+ with required dependencies installed
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- Appropriate authorization for any testing activities
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## Instructions
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1. Install dependencies: `pip install python-evtx lxml`
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2. Collect PowerShell Operational logs: `Microsoft-Windows-PowerShell%4Operational.evtx`
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3. Parse Event ID 4104 entries using python-evtx to extract ScriptBlockText, ScriptBlockId, and MessageNumber/MessageTotal for multi-part script reconstruction.
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4. Apply detection heuristics:
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- Base64-encoded commands (`-EncodedCommand`, `FromBase64String`)
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- Download cradles (`DownloadString`, `DownloadFile`, `Invoke-WebRequest`, `Net.WebClient`)
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- AMSI bypass patterns (`AmsiUtils`, `amsiInitFailed`)
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- Obfuscation indicators (high entropy, tick-mark insertion, string concatenation)
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5. Generate a report with reconstructed scripts, risk scores, and MITRE ATT&CK mappings.
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```bash
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python scripts/agent.py --evtx-file /path/to/PowerShell-Operational.evtx --output ps_analysis.json
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```
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## Examples
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### Detect Encoded Command Execution
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```python
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import base64
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if "-encodedcommand" in script_text.lower():
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encoded = script_text.split()[-1]
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decoded = base64.b64decode(encoded).decode("utf-16-le")
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```
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### Reconstruct Multi-Block Script
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Scripts split across multiple 4104 events share a `ScriptBlockId`. Concatenate blocks ordered by `MessageNumber` to recover the full script.
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