Anthropic-Cybersecurity-Skills/skills/analyzing-ransomware-network-indicators/SKILL.md

name, description, domain, subdomain, tags, version, author, license, d3fend_techniques, nist_csf, mitre_attack, mitre_f3

name	description	domain	subdomain	tags	version	author	license	d3fend_techniques	nist_csf	mitre_attack	mitre_f3
analyzing-ransomware-network-indicators	Identify ransomware-related network indicators, including C2 beaconing patterns, TOR exit node connections, data exfiltration flows, and encryption key exchange, by analyzing Zeek conn.log and NetFlow data. Use when threat hunting for active ransomware network activity or investigating suspected pre-encryption exfiltration during incident response.	cybersecurity	threat-hunting	ransomware c2-beaconing zeek netflow tor exfiltration network-forensics	1.0	mahipal	Apache-2.0	File Metadata Consistency Validation Certificate Analysis Application Protocol Command Analysis Content Format Conversion File Content Analysis	DE.CM-01 DE.AE-02 DE.AE-07 ID.RA-05	T1071.001 T1573 T1048 T1567.002 T1486	version tactics techniques 1.1 positioning monetization id name tactic source T1219 Remote Access Tools positioning attack id name tactic source F1018 Convert to Cryptocurrency monetization f3 id name tactic source F1047 Transfer of funds monetization f3

Analyzing Ransomware Network Indicators

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

1. Parse Connection Logs — Ingest Zeek conn.log (TSV) or NetFlow records into structured format
2. Detect Beaconing Patterns — Calculate connection interval statistics (mean, stddev, coefficient of variation) to identify periodic callbacks
3. Check TOR Exit Node Connections — Cross-reference destination IPs against current TOR exit node list
4. Identify Data Exfiltration — Flag connections with unusually high outbound byte ratios to external IPs
5. Analyze DNS Patterns — Detect DGA-like domain queries and high-entropy subdomains
6. Score and Correlate — Apply composite risk scoring across all indicator types
7. 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)