detecting-command-and-control-over-dns

# Detecting Command and Control Over DNS ## When to Use - Investigating suspected DNS tunneling used for C2 communication or data exfiltration - Analyzing DNS query logs for signs of encoded payloads in subdomain strings - Classifying domains as DGA-generated vs. legitimate using statistical or ML methods - Detecting DNS beaconing patterns (regular intervals, consistent query sizes) - Hunting for Iodine, dnscat2, dns2tcp, Cobalt Strike DNS, or Sliver DNS traffic - Monitoring TXT record abuse for command delivery or staged payload download - Building DNS anomaly detection rules for SOC/SIEM deployment **Do not use** for general DNS performance monitoring or DNS configuration auditing; use DNS health monitoring tools for those. For HTTP/HTTPS-based C2 detection, use network traffic analysis skills focused on web protocols. **DISCLAIMER**: DNS tunneling tools referenced in this skill (Iodine, dnscat2, dns2tcp) are dual-use. They have legitimate uses (bypassing captive portals, security research) and malicious uses (C2 channels, exfiltration). Only deploy detection in networks you are authorized to monitor. Testing tunneling tools requires explicit authorization. ## Prerequisites - DNS query logs from recursive resolver, Zeek/Bro, Suricata, or passive DNS tap - Python 3.9+ with `numpy`, `scikit-learn`, `pandas`, `tldextract`, and `dnspython` - Zeek (formerly Bro) with dns.log output or Suricata with DNS EVE JSON logging - SIEM access (Splunk, Elastic, Microsoft Sentinel) fo...