ReddRadar
Agent skill
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.
Install this agent skill to your Project
npx add-skill https://github.com/autohandai/community-skills/tree/main/analyzing-powershell-script-block-logging
SKILL.md
Instructions
- Install dependencies:
pip install python-evtx lxml - Collect PowerShell Operational logs:
Microsoft-Windows-PowerShell%4Operational.evtx - Parse Event ID 4104 entries using python-evtx to extract ScriptBlockText, ScriptBlockId, and MessageNumber/MessageTotal for multi-part script reconstruction.
- 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)
- Base64-encoded commands (
- Generate a report with reconstructed scripts, risk scores, and MITRE ATT&CK mappings.
python scripts/agent.py --evtx-file /path/to/PowerShell-Operational.evtx --output ps_analysis.json
Examples
Detect Encoded Command Execution
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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