DNS And Internet Assets: Hidden Risks In PCI Compliance

When a retailer’s bank and credit card services are tied to a global financial institution, any cyberattack on that bank’s infrastructure isn’t just their problem—it’s yours.

PCI DSS mandates security over all Internet-facing systems, and that includes critical DNS assets. Yet, all too often, DNS and external-facing infrastructure are overlooked in compliance checklists. In the wake of a major cyberattack, such as the recent cyberattack on Marks and Spencer, attackers can exploit DNS weaknesses to redirect traffic, intercept cardholder data, or knock out access to payment systems entirely.

PCI DSS v4.0 is clear: if it touches the cardholder data environment or supports it—like external DNS—it must be protected and tested. Retailers can’t afford to ignore the upstream risk. In a hyper-connected ecosystem, your security and PII data exposure to cybercrime, fraud, and loss is only as strong as the bank’s exposed and insecure vulnerabilities.

You Should Know:

1. DNS Security Best Practices

DNSSEC (DNS Security Extensions): Prevents DNS spoofing by digitally signing DNS records.
```
dig example.com +dnssec 
```
Regular DNS Audits: Use tools like nslookup, dig, and `whois` to check DNS configurations.
```
nslookup example.com 
whois example.com 
```
Monitor DNS Changes: Implement tools like DNSWatch or Cisco Umbrella to detect unauthorized changes.

2. PCI DSS v4.0 Key Requirements for DNS

Requirement 1.2.3: Verify that DNS servers are securely configured.
Requirement 11.4: Perform penetration testing on DNS infrastructure.
Requirement 12.10: Ensure third-party DNS providers comply with PCI DSS.

Linux & Windows Commands for DNS Security Checks

Linux:

 Check DNS resolution time 
time dig example.com

Test for DNS cache poisoning 
dnsenum --enum example.com

Verify DNSSEC validation 
delv example.com

Windows:

 Check DNS records 
Resolve-DnsName example.com

Test DNS server response time 
Measure-Command { Resolve-DnsName example.com }

Verify DNSSEC with PowerShell 
Get-DnsClientDnsSecValidation

4. Mitigating DNS Attacks

Prevent DNS Tunneling: Use Splunk or Zeek to monitor unusual DNS traffic.
Block Malicious Domains: Update firewall rules to block known malicious DNS servers.
```
iptables -A OUTPUT -p udp --dport 53 -j DROP -d malicious-dns.com 
```

Enable DNS Logging:

journalctl -u systemd-resolved --no-pager

What Undercode Say:

DNS is often the weakest link in cybersecurity, yet it is frequently overlooked in compliance audits. PCI DSS v4.0 now explicitly includes DNS security, meaning businesses must take proactive steps to harden their DNS infrastructure. Regular audits, DNSSEC implementation, and real-time monitoring are no longer optional—they are critical for preventing data breaches and financial fraud.

Expected Output:

A hardened DNS configuration with DNSSEC.
Regular penetration testing reports for DNS infrastructure.
Automated monitoring for unauthorized DNS changes.
Blocklists for malicious DNS servers.

For further reading:

References:

Reported By: Andy Jenkinson – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅

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