Analyzing DNS Logs for Exfiltration

When to Use

Use this skill when:

• SOC teams suspect data exfiltration through DNS tunneling to bypass firewall/proxy controls
• Threat intelligence indicates adversaries using DNS-based C2 channels (e.g., Cobalt Strike DNS beacon)
• UEBA detects anomalous DNS query volumes from specific hosts
• Malware analysis reveals DNS-over-HTTPS (DoH) or DNS tunneling capabilities

Do not use for standard DNS troubleshooting or availability monitoring — this skill focuses on security-relevant DNS abuse detection.

Prerequisites

• DNS query logging enabled (Windows DNS Server, Bind, Infoblox, or Cisco Umbrella)
• DNS logs ingested into SIEM (Splunk with Stream:DNS, dns sourcetype, or Zeek DNS logs)
• Passive DNS data for historical domain resolution analysis
• Baseline of normal DNS behavior (query volume, domain distribution, TXT record frequency)
• Python with math and collections libraries for entropy calculation