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Threat actor infrastructure tracking involves monitoring and mapping adversary-controlled assets including command-and-control (C2) servers, phishing domains, exploit kit hosts, bulletproof hosting, and staging servers. This skill covers using passive DNS, certificate transparency logs, Shodan/Censys scanning, WHOIS analysis, and network fingerprinting to discover, track, and pivot across threat actor infrastructure over time.
When to Use
When managing security operations that require tracking threat actor infrastructure
When improving security program maturity and operational processes
When establishing standardized procedures for security team workflows
When integrating threat intelligence or vulnerability data into operations
Prerequisites
Python 3.9+ with shodan, censys, requests, stix2 libraries
API keys: Shodan, Censys, VirusTotal, SecurityTrails, PassiveTotal
Understanding of DNS, TLS/SSL certificates, IP allocation, ASN structure
Familiarity with passive DNS and certificate transparency concepts
Access to domain registration (WHOIS) lookup services
Key Concepts
Infrastructure Pivoting
Pivoting is the technique of using one known indicator to discover related infrastructure. Starting from a known C2 IP address, analysts can pivot via: passive DNS (find domains), reverse WHOIS (find related registrations), SSL certificates (find shared certs), SSH key fingerprints, HTTP response fingerprints, JARM/JA3S hashes, and WHOIS registrant data.
Passive DNS
Passive DNS databases record DNS query/response data observed at recursive resolvers. This allows analysts to find historical domain-to-IP mappings, discover domains hosted on a known C2 IP, and identify fast-flux or domain generation algorithm (DGA) behavior.
Certificate Transparency
Certificate Transparency (CT) logs publicly record all SSL/TLS certificates issued by CAs. Monitoring CT logs reveals new certificates registered for suspicious domains, helping identify phishing sites and C2 infrastructure before they become active.
Network Fingerprinting
JARM: Active TLS server fingerprint (hash of TLS handshake responses)
JA3S: Passive TLS server fingerprint (hash of Server Hello)
HTTP Headers: Server banners, custom headers, response patterns
Favicon Hash: Hash of HTTP favicon for server identification
