Anthropic-Cybersecurity-Skills/skills/detecting-suspicious-powershell-execution/references/workflows.md

Detailed Hunting Workflow - Detecting Suspicious Powershell Execution

Phase 1: Data Collection and Querying

Splunk SPL Query

index=sysmon EventCode=1 Image="*\\powershell.exe"
| where match(CommandLine, "(?i)(-enc|-encodedcommand|-w hidden|-nop|iex|invoke-expression|downloadstring|webclient|bypass)")
| table _time Computer User CommandLine ParentImage

KQL Query (Microsoft Defender for Endpoint)

DeviceProcessEvents
| where FileName =~ "powershell.exe"
| where ProcessCommandLine has_any ("-enc","-encodedcommand","-w hidden","iex","downloadstring","bypass")
| project Timestamp, DeviceName, AccountName, ProcessCommandLine, InitiatingProcessFileName

Phase 2: Baseline and Anomaly Detection

Step 2.1 - Establish Normal Behavior Baseline

• Collect 30 days of historical data for the targeted technique
• Document expected patterns, frequencies, and legitimate use cases
• Identify known false positive sources and document exceptions
• Build statistical baseline (mean, standard deviation) for key metrics

Step 2.2 - Identify Anomalies

• Compare current activity against the 30-day baseline
• Flag events exceeding 3 standard deviations from normal
• Prioritize anomalies by risk score and potential business impact
• Cross-reference with threat intelligence for known IOCs

Phase 3: Investigation and Correlation

Step 3.1 - Deep Dive Analysis

• For each anomaly, collect full process tree context
• Correlate with network activity, file operations, and authentication events
• Check binary signatures, file hashes, and certificate validity
• Review user account context and access patterns

Step 3.2 - Attack Chain Reconstruction

• Map findings to MITRE ATT&CK kill chain stages
• Identify initial access vector if applicable
• Trace lateral movement and privilege escalation paths
• Determine data access and potential exfiltration

Phase 4: Validation and Response

Step 4.1 - True/False Positive Determination

• Verify findings with system owners and IT operations
• Check change management records for authorized activities
• Validate user context (authorized actions vs. compromised account)
• Document determination rationale for each finding

Step 4.2 - Response Actions

• For confirmed threats: initiate incident response procedures
• For detection gaps: create or update detection rules
• For false positives: tune existing rules and update exclusions
• Update threat hunting playbook with lessons learned

Phase 5: Documentation and Reporting

Step 5.1 - Hunt Report

• Summarize hypothesis, methodology, and findings
• Include all queries executed and their results
• Document IOCs discovered and detection rules created
• Provide recommendations for security improvements

Step 5.2 - Knowledge Base Update

• Add findings to threat intelligence platform
• Update MITRE ATT&CK coverage heatmap
• Share detection rules via Sigma format
• Schedule follow-up hunts for related techniques