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detecting-suspicious-powershell-execution

Hunt for suspicious PowerShell execution (T1059.001) such as encoded commands, download cradles, AMSI bypass, and constrained language mode evasion using EDR telemetry (CrowdStrike, Microsoft Defender for Endpoint), Sysmon, and SIEM queries (Splunk, Elastic). Use when proactively threat hunting, triaging EDR/SIEM alerts, or scoping an incident involving malicious PowerShell activity.

Published by mukul975 ↗mukul975/Anthropic-Cybersecurity-Skills

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Use detecting-suspicious-powershell-execution to perform an authorized hypothesis-driven hunt for suspicious PowerShell execution, including encoded commands, download cradles, AMSI bypass, and constrained-language evasion, then produce the documented Hunt ID report for [EDR/SIEM platform, authorized Windows scope, time window, and relevant alerts or IOCs].

Required inputs

[EDR/SIEM platform, authorized Windows scope, time window, and relevant alerts or IOCs]

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SKILL.md

name: detecting-suspicious-powershell-executiondescription: Hunt for suspicious PowerShell execution (T1059.001) such as encoded commands,  download cradles, AMSI bypass, and constrained language mode evasion using EDR telemetry  (CrowdStrike, Microsoft Defender for Endpoint), Sysmon, and SIEM queries (Splunk, Elastic).  Use when proactively threat hunting, triaging EDR/SIEM alerts, or scoping an incident  involving malicious PowerShell activity.domain: cybersecuritysubdomain: threat-huntingtags: - threat-hunting- mitre-attack- powershell- execution- t1059- amsi- proactive-detectionversion: '1.0'author: mahipallicense: Apache-2.0d3fend_techniques: - Executable Denylisting- Execution Isolation- File Metadata Consistency Validation- Content Format Conversion- File Content Analysisnist_csf: - DE.CM-01- DE.AE-02- DE.AE-07- ID.RA-05mitre_attack: - T1059.001- T1027.010- T1620- T1105

Detecting Suspicious Powershell Execution

When to Use

When proactively hunting for indicators of detecting suspicious powershell execution in the environment
After threat intelligence indicates active campaigns using these techniques
During incident response to scope compromise related to these techniques
When EDR or SIEM alerts trigger on related indicators
During periodic security assessments and purple team exercises

Prerequisites

EDR platform with process and network telemetry (CrowdStrike, MDE, SentinelOne)
SIEM with relevant log data ingested (Splunk, Elastic, Sentinel)
Sysmon deployed with comprehensive configuration
Windows Security Event Log forwarding enabled
Threat intelligence feeds for IOC correlation

Workflow

Formulate Hypothesis: Define a testable hypothesis based on threat intelligence or ATT&CK gap analysis.
Identify Data Sources: Determine which logs and telemetry are needed to validate or refute the hypothesis.
Execute Queries: Run detection queries against SIEM and EDR platforms to collect relevant events.
Analyze Results: Examine query results for anomalies, correlating across multiple data sources.
Validate Findings: Distinguish true positives from false positives through contextual analysis.
Correlate Activity: Link findings to broader attack chains and threat actor TTPs.
Document and Report: Record findings, update detection rules, and recommend response actions.

Key Concepts

Concept	Description
T1059.001	PowerShell
T1059.003	Windows Command Shell
T1562.001	Disable or Modify Tools

Tools & Systems

Tool	Purpose
CrowdStrike Falcon	EDR telemetry and threat detection
Microsoft Defender for Endpoint	Advanced hunting with KQL
Splunk Enterprise	SIEM log analysis with SPL queries
Elastic Security	Detection rules and investigation timeline
Sysmon	Detailed Windows event monitoring
Velociraptor	Endpoint artifact collection and hunting
Sigma Rules	Cross-platform detection rule format

Common Scenarios

Scenario 1: Base64 encoded PowerShell command launched by macro document
Scenario 2: IEX download cradle fetching payload from C2 server
Scenario 3: AMSI bypass via reflection patching before payload execution
Scenario 4: PowerShell Empire agent communicating with C2

Output Format

Hunt ID: TH-DETECT-[DATE]-[SEQ]
Technique: T1059.001
Host: [Hostname]
User: [Account context]
Evidence: [Log entries, process trees, network data]
Risk Level: [Critical/High/Medium/Low]
Confidence: [High/Medium/Low]
Recommended Action: [Containment, investigation, monitoring]