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Anthropic-Cybersecurity-Skills/skills/performing-dns-tunneling-detection/SKILL.md
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mukul975 cb8d79e068 Map all 754 skills to MITRE ATT&CK v19.1
- Add validated mitre_attack frontmatter to all 754 skills (286 distinct
  techniques), verified against MITRE ATT&CK v19.1 via the official
  mitreattack-python library: 0 revoked, deprecated, or invalid IDs
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  threat-intel, and red-team skills (e.g. DCSync -> T1003.006,
  Kerberoasting -> T1558.003, Pass-the-Ticket -> T1550.003)
- Reconcile v19.1 tactic restructuring: Defense Evasion split into
  Stealth (TA0005) and Defense Impairment (TA0112); revoked T1562.*
  family and T1070.001/.002 remapped to active equivalents (T1685.*)
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  stopword tags, add semantic cybersecurity tags)
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2026-06-01 12:13:29 +02:00

2.5 KiB

name, description, domain, subdomain, tags, version, author, license, nist_csf, mitre_attack
name description domain subdomain tags version author license nist_csf mitre_attack
performing-dns-tunneling-detection Detects DNS tunneling by computing Shannon entropy of DNS query names, analyzing query length distributions, inspecting TXT record payloads, and identifying high subdomain cardinality. Uses scapy for packet capture analysis and statistical methods to distinguish legitimate DNS from covert channels. Use when hunting for data exfiltration. cybersecurity security-operations
dns-tunneling
exfiltration-detection
shannon-entropy
dns-analysis
threat-detection
security-operations
1.0 mahipal Apache-2.0
DE.CM-01
RS.MA-01
GV.OV-01
DE.AE-02
T1078
T1190
T1059
T1048
T1041

Performing DNS Tunneling Detection

When to Use

  • When conducting security assessments that involve performing dns tunneling detection
  • When following incident response procedures for related security events
  • When performing scheduled security testing or auditing activities
  • When validating security controls through hands-on testing

Prerequisites

  • Familiarity with security operations concepts and tools
  • Access to a test or lab environment for safe execution
  • Python 3.8+ with required dependencies installed
  • Appropriate authorization for any testing activities

Instructions

Analyze DNS traffic for indicators of DNS tunneling using entropy analysis and statistical methods on query name characteristics.

import math
from collections import Counter

def shannon_entropy(data):
    if not data:
        return 0
    counter = Counter(data)
    length = len(data)
    return -sum((c/length) * math.log2(c/length) for c in counter.values())

# Legitimate domain: low entropy (~3.0-3.5)
print(shannon_entropy("www.google.com"))
# DNS tunnel: high entropy (~4.0-5.0)
print(shannon_entropy("aGVsbG8gd29ybGQ.tunnel.example.com"))

Key detection indicators:

  1. High Shannon entropy in query names (> 3.5 for subdomain labels)
  2. Unusually long query names (> 50 characters)
  3. High volume of TXT record requests to a single domain
  4. High unique subdomain count per parent domain
  5. Non-standard character distribution in labels

Examples

from scapy.all import rdpcap, DNS, DNSQR
packets = rdpcap("dns_traffic.pcap")
for pkt in packets:
    if pkt.haslayer(DNSQR):
        query = pkt[DNSQR].qname.decode()
        entropy = shannon_entropy(query)
        if entropy > 4.0:
            print(f"Suspicious: {query} (entropy={entropy:.2f})")