Dangling DNS: Understanding the hidden threat to your domain security

In fast-moving environments, DNS updates can fall through the cracks. Without consistent oversight, even well-equipped teams can overlook critical changes, leaving the door open for cybercriminals.

Why do dangling DNS records matter?

Dangling DNS records are a real and growing cyber risk. Cybercriminals can exploit them to hijack subdomains, impersonate brands, or launch phishing attacks that appear legitimate to unsuspecting users.

Key DNS dangling risks include:

• Email spoofing and abuse: Compromised subdomains could potentially bypass your organization's protections, enabling attackers to send fraudulent emails that appear legitimate.
• Data breaches: Users who trust your business's subdomain might interact with malicious emails, potentially exposing sensitive internal or customer data.
• Reputational damage: If your brand is used in phishing campaigns or spoofing scams, trust can quickly vanish among customers, partners, and the public, leading to long-term reputational damage.

A study conducted between 2020 and 2023 identified 20 904 subdomain hijacks globally that contained malicious content. This shows how necessary it is for companies to adopt preventive measures before vulnerabilities are discovered and exploited.

How do dangling DNS records happen?

Dangling DNS vulnerabilities typically originate from mismanagement or oversight. Below are common causes.

Many businesses struggle with limited visibility into DNS configurations across teams. As a result, outdated records can go undetected for months – or even years – until they're either discovered by the company or exploited by attackers.

Real-world examples of dangling DNS

In 2023, researchers showed how even major international organizations are vulnerable to dangling DNS. These included government bodies, top universities (like UCLA and Stanford), global media outlets (such as CNN), and financial institutions.

When attackers exploit these vulnerabilities, they can expose users to a range of serious threats, including:

• Malware distribution: Hijacked subdomains can be used to distribute malicious software, potentially compromising recipient systems and networks.
• Misinformation spread: Threat actors can exploit the credibility of reputable institutions to spread false or misleading information.
• Phishing attacks: Attackers can create convincing phishing emails from the trusted subdomain to trick users into revealing credentials or sensitive data.

How to detect and prevent dangling DNS

Proactive management and continuous monitoring are key to reducing the risk of a dangling DNS record.

Follow these best practices to secure your business's DNS:

• Conduct regular DNS audits: Routinely review all DNS records, especially after deactivating services or updating third-party tools.
• Use automated monitoring features: Use tools that scan and alert your company to DNS record changes. Automated monitoring helps identify issues before attackers do.
• Promote education and enforce policies: Train internal teams on the risks tied to DNS hygiene and implement formal DNS management policies. These policies should clarify roles and ensure accountability.

Protect your brand from dangling DNS risks

Do not let a simple oversight lead to phishing, impersonation, or data breaches. Sendmarc's email security solutions provide automated monitoring, full visibility, and advanced protection against email-based threats, including some of those enabled by DNS vulnerabilities.

Our platform helps your business close security gaps, maintain compliance, and reduce operational risk, giving your team more time to focus on strategic initiatives. With continuous updates, expert support, and actionable insights, Sendmarc ensures your company's domain stays protected as its infrastructure evolves.

Whether you're managing one domain or a hundred, Sendmarc helps ensure that your organization's DNS environment remains clean, secure, and trustworthy.