Anthropic-Cybersecurity-Skills/skills/hunting-for-unusual-network-connections/references/workflows.md

Detailed Hunting Workflow - Hunting For Unusual Network Connections

Phase 1: Data Collection and Querying

Splunk SPL Query

index=sysmon EventCode=3
| where NOT match(DestinationIp, "^(10\\.|172\\.(1[6-9]|2[0-9]|3[01])\\.|192\\.168\\.)")
| stats count dc(DestinationIp) as unique_ips values(DestinationPort) as ports by Image Computer
| where count > 50 OR unique_ips > 10
| sort -count

KQL Query (Microsoft Defender for Endpoint)

DeviceNetworkEvents
| where RemoteIPType == "Public"
| summarize ConnectionCount=count(), UniqueIPs=dcount(RemoteIP), Ports=make_set(RemotePort) by InitiatingProcessFileName, DeviceName
| where ConnectionCount > 50 or UniqueIPs > 10

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