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Anthropic-Cybersecurity-Skills/skills/analyzing-powershell-script-block-logging/references/api-reference.md
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mukul975 27c6414ca5 Add folder anatomy (scripts/agent.py + references/api-reference.md) for 648 cybersecurity skills
Complete skill folder anatomy across all cybersecurity skills:
- scripts/agent.py: 80-150 line Python agents using real libraries (impacket,
  boto3, azure-mgmt-*, kubernetes, pefile, yara, scapy, shodan, stix2, etc.)
- references/api-reference.md: real API documentation with method signatures
- LICENSE: MIT license for all skill folders
2026-03-10 21:02:12 +01:00

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# API Reference: PowerShell Script Block Logging Analysis
## python-evtx Library
### FileHeader
```python
from Evtx.Evtx import FileHeader
with open(evtx_path, "rb") as f:
fh = FileHeader(f)
for record in fh.records():
xml_string = record.xml() # Returns XML string of the event
```
### Event XML Structure (Event ID 4104)
```xml
<Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
<System>
<EventID>4104</EventID>
<TimeCreated SystemTime="2024-01-15T10:30:00.000Z"/>
</System>
<EventData>
<Data Name="MessageNumber">1</Data>
<Data Name="MessageTotal">3</Data>
<Data Name="ScriptBlockText">...powershell code...</Data>
<Data Name="ScriptBlockId">guid-string</Data>
<Data Name="Path">C:\script.ps1</Data>
</EventData>
</Event>
```
## lxml etree Parsing
```python
from lxml import etree
NS = {"evt": "http://schemas.microsoft.com/win/2004/08/events/event"}
root = etree.fromstring(xml_bytes)
event_id = root.find(".//evt:System/evt:EventID", NS).text
data_elems = root.findall(".//evt:EventData/evt:Data", NS)
for elem in data_elems:
name = elem.get("Name")
value = elem.text
```
## Script Block Reconstruction
Large PowerShell scripts are split across multiple Event 4104 entries:
- `ScriptBlockId`: Unique GUID shared across all parts
- `MessageNumber`: Part index (1-based)
- `MessageTotal`: Total number of parts
- Reconstruct: concatenate parts ordered by MessageNumber
## Key Detection Patterns
| Pattern | MITRE | Risk |
|---------|-------|------|
| `-EncodedCommand` | T1059.001 | High |
| `FromBase64String` | T1140 | High |
| `Invoke-Expression` / `iex` | T1059.001 | High |
| `DownloadString` / `Net.WebClient` | T1105 | Critical |
| `AmsiUtils` / `amsiInitFailed` | T1562.001 | Critical |
| `Invoke-Mimikatz` | T1003 | Critical |
| High entropy (>5.5) | T1027 | Medium |