What it does. Hunts for DNS-based persistence mechanisms such as DNS hijacking, dangling Part of mukul975/Anthropic-Cybersecurity-Skills (817 security skills) (mukul975/Anthropic-Cybersecurity-Skills).

Install

• npx skills add mukul975/Anthropic-Cybersecurity-Skills --skill hunting-for-dns-based-persistence, or copy the skill folder into ~/.claude/skills/hunting-for-dns-based-persistence/.
• Raw file: curl -sL https://raw.githubusercontent.com/mukul975/Anthropic-Cybersecurity-Skills/HEAD/skills/hunting-for-dns-based-persistence/SKILL.md

SKILL.md (verbatim)

name: hunting-for-dns-based-persistence
description: Hunts for DNS-based persistence mechanisms such as DNS hijacking, dangling
  CNAME records enabling subdomain takeover, wildcard DNS abuse, and unauthorized zone
  or NS delegation changes, using passive DNS history (SecurityTrails API), Route53/Azure
  DNS/Cloudflare audit logs, and zone transfer analysis. Use when investigating suspected
  DNS hijacking or subdomain takeover, or when threat hunting for DNS record tampering
  that persists across credential rotations and endpoint reimaging.
domain: cybersecurity
subdomain: threat-hunting
tags:
- dns
- persistence
- threat-hunting
- passive-dns
- dns-hijacking
- subdomain-takeover
- securitytrails
version: '1.0'
author: mahipal
license: Apache-2.0
nist_csf:
- DE.CM-01
- DE.AE-02
- DE.AE-07
- ID.RA-05
mitre_attack:
- T1046
- T1057
- T1082
- T1083
- T1547

Hunting for DNS-based Persistence

Overview

Attackers establish DNS-based persistence by hijacking DNS records, creating unauthorized subdomains, abusing wildcard DNS entries, or modifying NS delegations to redirect traffic through attacker-controlled infrastructure. These techniques survive credential rotations, endpoint reimaging, and traditional remediation because DNS changes persist independently of compromised hosts. Detection requires passive DNS historical analysis, zone file auditing, and monitoring for unauthorized record modifications. This skill covers hunting methodologies using SecurityTrails passive DNS API, DNS audit logs from Route53/Azure DNS/Cloudflare, and zone transfer analysis.

When to Use

• When investigating security incidents that require hunting for dns based persistence
• 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

• SecurityTrails API key (free tier provides 50 queries/month)
• Access to DNS provider audit logs (Route53, Azure DNS, Cloudflare, or on-premises DNS)
• Python 3.9+ with requests library
• DNS zone file access or AXFR capability for internal zones
• Historical DNS baseline for comparison

Steps

Step 1: Baseline DNS Records

Export current DNS zone records and establish baseline for all authorized A, AAAA, CNAME, MX, NS, and TXT records.

Step 2: Query Passive DNS History

Use SecurityTrails API to retrieve historical DNS records and identify unauthorized changes, new subdomains, and CNAME records pointing to decommissioned services (dangling CNAMEs).

Step 3: Detect Anomalies

Compare current records against baseline to identify unauthorized modifications, wildcard records that resolve all subdomains, NS delegation changes, and MX record hijacking.

Step 4: Investigate Findings

Correlate DNS anomalies with threat intelligence feeds, check resolution targets against known malicious infrastructure, and validate record ownership.

Expected Output

JSON report listing DNS anomalies with record type, historical changes, risk severity, and remediation recommendations for each finding.

Other files in this skill

• LICENSE
• references/api-reference.md
• scripts/agent.py

references/api-reference.md (verbatim)

5 placeholder credentials shortened to pass the site's secret filter.

API Reference: Hunting for DNS-based Persistence

SecurityTrails API

# Get current DNS records
curl -s "https://api.securitytrails.com/v1/domain/example.com" \
  -H "APIKEY: YOUR_KEY

# Get subdomains
curl -s "https://api.securitytrails.com/v1/domain/example.com/subdomains" \
  -H "APIKEY: YOUR_KEY

# Historical A records
curl -s "https://api.securitytrails.com/v1/history/example.com/dns/a" \
  -H "APIKEY: YOUR_KEY

# Historical NS records
curl -s "https://api.securitytrails.com/v1/history/example.com/dns/ns" \
  -H "APIKEY: YOUR_KEY

# WHOIS history
curl -s "https://api.securitytrails.com/v1/history/example.com/whois" \
  -H "APIKEY: YOUR_KEY

DNS Record Types to Hunt

Dangling CNAME Services (Subdomain Takeover)

dig Commands for Hunting

# Check all record types
dig ANY example.com +noall +answer

# Test for wildcard records
dig A randomtest123.example.com +short

# Check NS delegation chain
dig NS example.com +trace

# Verify DNSSEC
dig DNSKEY example.com +dnssec +short

# Check for zone transfer (authorized testing only)
dig AXFR example.com @ns1.example.com

MITRE ATT&CK DNS Techniques

References

• SecurityTrails API: https://securitytrails.com/corp/api
• Can I Take Over XYZ: https://github.com/EdOverflow/can-i-take-over-xyz
• Passive DNS databases: https://www.farsightsecurity.com/solutions/dnsdb/

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