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DNS Security — How Attackers Exploit Your Domain Configuration

Unmasking DNS threats: What attackers see that you don't.

AttackVector Team

AttackVector Team

Security Researchers

|February 5, 20268 min read

Summary

Explore how attackers exploit DNS configurations to infiltrate systems. From DNS mechanics to attacks like cache poisoning and subdomain takeovers, understand vulnerabilities and defense strategies. Discover how AttackVector's AI-driven audits can strengthen your DNS defenses.

ELI5 — The Simple Version

Think of DNS as the internet’s phonebook. When you type a website’s name, DNS finds the number (IP address) for you. But if someone tampers with this phonebook, you might end up calling the wrong number—a malicious website instead of the one you wanted. Attackers exploit these misconfigurations by copying pages to trick you or altering records to intercept your emails. Like a prankster changing numbers in a phonebook, attackers change DNS records to reroute you or steal your info.

The Hidden World of DNS Vulnerabilities

Remember the Equifax breach? It wasn't just poor patch management; attackers also exploited DNS misconfigurations to move laterally. DNS, often overlooked, can become a threat if mishandled.

What is DNS?

DNS translates human-friendly domain names like example.com into IP addresses. It's like a phonebook, connecting names to numbers. If attackers alter these records, they can redirect users to malicious sites, intercept emails, or take control of subdomains.

Zone Transfer Leaks: A Backdoor for Attackers

Zone transfer leaks occur when DNS servers allow unauthorized data transfers, exposing DNS records to attackers. In 2016, a DNS zone transfer misconfiguration exposed sensitive information of a financial institution, leading to data theft.

Testing for Zone Transfer Leaks:

  1. 1Use dig to attempt a zone transfer:
dig axfr @nameserver example.com
  1. 1Ensure your DNS server restricts zone transfers to trusted IPs only.

Subdomain Takeover: The Ghost Domains

A subdomain takeover occurs when a subdomain points to an external service no longer in use. Attackers can claim the service and host malicious content. A major tech company once forgot to remove a CNAME record pointing to an expired GitHub page, falling victim to this.

DNS Cache Poisoning: Misdirection at Its Finest

This attack tricks DNS servers into caching false information. The Kaminsky bug (CVE-2008-1447) highlighted how devastating cache poisoning can be, redirecting users to phishing sites and harvesting credentials on a massive scale.

Typosquatting: Exploiting Human Error

Typosquatting involves registering domains that are misspelled versions of popular sites. Attackers rely on mistyped URLs to lure users to malicious sites. A classic example is goggle.com, used for phishing attacks.

Dangling CNAME Records: A Forgotten Threat

Dangling CNAME records occur when a CNAME points to a non-existent domain. Attackers can register the domain and control the subdomain, often found during DNS audits.

Email Security: SPF, DKIM, and DMARC

Email spoofing attacks are rampant, but SPF, DKIM, and DMARC records can mitigate these. SPF specifies which mail servers can send emails for your domain. DKIM signs emails to verify authenticity. DMARC aligns SPF and DKIM policies, reducing phishing risks.

How AttackVector Enhances DNS Security

At AttackVector, we use AI to perform comprehensive DNS audits. Our process includes:

  • Record Enumeration: Identifying all DNS records to spot misconfigurations.
  • Subdomain Discovery: Uncovering hidden subdomains that could be vulnerable.
  • DNSSEC Validation: Ensuring DNS records are authenticated and integrity-checked.
  • Zone Transfer Testing: Checking for unauthorized data transfers.
  • Email Security Checks: Verifying SPF, DKIM, and DMARC configurations to prevent spoofing.

Actionable Insights

  1. 1Run regular DNS audits using tools like nmap and dnsenum to uncover vulnerabilities.
  2. 2Implement DNSSEC to authenticate your DNS queries and responses.
  3. 3Restrict zone transfers to trusted IPs only to prevent data leaks.
  4. 4Monitor subdomain records to avoid takeovers and dangling CNAMEs.
  5. 5Configure SPF, DKIM, and DMARC for robust email security.

Key Takeaways

  • 1Run regular DNS audits using tools like nmap and dnsenum.
  • 2Implement DNSSEC to authenticate DNS queries and responses.
  • 3Restrict zone transfers to trusted IPs only.
  • 4Monitor subdomain records to avoid takeovers and dangling CNAMEs.
  • 5Configure SPF, DKIM, and DMARC for robust email security.

Referenced CVEs

CVE-2008-1447