analyzing-powershell-script-block-logging
Parse Windows PowerShell Script Block Logs (Event ID 4104) from EVTX files to detect obfuscated commands, encoded payloads, and living-off-the-land techniques. Uses python-evtx to extract and reconstruct multi-block scripts, applies entropy analysis and pattern matching for Base64-encoded commands, Invoke-Expression abuse, download cradles, and AMSI bypass attempts.
ソース情報
- リポジトリ
- AgentFlocks/flocks
- ソースの最終更新活動
- 2026年5月5日 05:45
- 検出された SKILL.md の言語
- 英語
- スター
- 488
- フォーク
- 93
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SKILL.md
ソースの指示 · 読み取り専用プレビュー- name
- analyzing-powershell-script-block-logging
- description
- Parse Windows PowerShell Script Block Logs (Event ID 4104) from EVTX files to detect obfuscated commands, encoded payloads, and living-off-the-land techniques. Uses python-evtx to extract and reconstruct multi-block scripts, applies entropy analysis and pattern matching for Base64-encoded commands, Invoke-Expression abuse, download cradles, and AMSI bypass attempts.
- domain
- cybersecurity
- subdomain
- security-operations
- tags
- ["powershell","script-block-logging","event-id-4104","obfuscation-detection","windows-forensics","endpoint-security"]
- version
- 1.0
- author
- mahipal
- license
- Apache-2.0
- nist_csf
- ["DE.CM-01","RS.MA-01","GV.OV-01","DE.AE-02"]
# Analyzing PowerShell Script Block Logging
## When to Use
- When investigating security incidents that require analyzing powershell script block logging
- When building detection rules or threat hunting queries for this domain
- When SOC analysts need structured procedures for this analysis type
- When validating security monitoring coverage for related attack techniques
## Prerequisites
- Familiarity with security operations concepts and tools
- Access to a test or lab environment for safe execution
- Python 3.8+ with required dependencies installed
- Appropriate authorization for any testing activities
## Instructions
1. Install dependencies: `pip install python-evtx lxml`
2. Collect PowerShell Operational logs: `Microsoft-Windows-PowerShell%4Operational.evtx`
3. Parse Event ID 4104 entries using python-evtx to extract ScriptBlockText, ScriptBlockId, and MessageNumber/MessageTotal for multi-part script reconstruction.
4. Apply detection heuristics:
- Base64-encoded commands (`-EncodedCommand`, `FromBase64String`)
- Download cradles (`DownloadString`, `DownloadFile`, `Invoke-WebRequest`, `Net.WebClient`)
- AMSI bypass patterns (`AmsiUtils`, `amsiInitFailed`)
- Obfuscation indicators (high entropy, tick-mark insertion, string concatenation)
5. Generate a report with reconstructed scripts, risk scores, and MITRE ATT&CK mappings.
```bash
python scripts/agent.py --evtx-file /path/to/PowerShell-Operational.evtx --output ps_analysis.json
```
## Examples
### Detect Encoded Command Execution
```python
import base64
if "-encodedcommand" in script_text.lower():
encoded = script_text.split()[-1]
decoded = base64.b64decode(encoded).decode("utf-16-le")
```
### Reconstruct Multi-Block Script
Scripts split across multiple 4104 events share a `ScriptBlockId`. Concatenate blocks ordered by `MessageNumber` to recover the full script.
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