Overview
Before and during ransomware execution, adversaries establish C2 channels, exfiltrate data, and download encryption keys. This skill analyzes Zeek conn.log and NetFlow data to detect beaconing patterns (regular-interval callbacks), connections to known TOR exit nodes, large outbound data transfers, and suspicious DNS activity associated with ransomware families.
When to Use
- When investigating security incidents that require analyzing ransomware network indicators
- When building detection rules or threat hunting queries for this domain
- When SOC analysts need structured procedures for this analysis type
- When validating security monitoring coverage for related attack techniques
Prerequisites
- Zeek conn.log files or NetFlow CSV/JSON exports
- Python 3.8+ with standard library
- TOR exit node list (fetched from Tor Project or threat intel feeds)
- Optional: Known ransomware C2 IOC list
Steps
- Parse Connection Logs — Ingest Zeek conn.log (TSV) or NetFlow records into structured format
- Detect Beaconing Patterns — Calculate connection interval statistics (mean, stddev, coefficient of variation) to identify periodic callbacks
- Check TOR Exit Node Connections — Cross-reference destination IPs against current TOR exit node list
- Identify Data Exfiltration — Flag connections with unusually high outbound byte ratios to external IPs
- Analyze DNS Patterns — Detect DGA-like domain queries and high-entropy subdomains
- Score and Correlate — Apply composite risk scoring across all indicator types
- Generate Report — Produce structured report with timeline and MITRE ATT&CK mapping
Expected Output
- JSON report with beaconing detections and interval statistics
- TOR exit node connection alerts
- Data exfiltration flow analysis
- Composite ransomware risk score with MITRE mapping (T1071, T1573, T1041)