In the rapidly evolving landscape of cybersecurity threats, hackers are honing in on a vulnerability known as “Dangling DNS” records to infiltrate corporate subdomains, putting organizations at risk of security breaches. This method of attack has gained traction among cybercriminals, underscoring the crucial need for ongoing vigilance in managing DNS configurations.
The concept of subdomain takeovers revolves around exploiting misconfigured or unused subdomains’ DNS entries, specifically CNAME records that point to defunct or expired services. By seizing control of these neglected subdomains, attackers can wreak havoc on an organization’s digital infrastructure. This type of attack, referred to as “Dangling DNS,” goes beyond CNAME records to encompass other DNS record types like NS, MX, A, and AAAA.
One common scenario involves terminating a service without updating corresponding DNS entries, enabling hackers to register the abandoned subdomain with the service provider and assume control. For instance, if a company discontinues a help desk subdomain hosted on a SaaS platform like Zendesk but neglects to update the DNS records, an attacker could exploit this oversight to manipulate traffic under the guise of the company’s subdomain.
Cloud service misconfigurations present another avenue for malicious activities. If an organization deletes a cloud resource such as an AWS S3 bucket meant for hosting a static website without updating or removing the associated DNS entries, cybercriminals can register a new bucket under the same subdomain to divert and potentially tamper with web traffic.
A recent research study spanning from October 2024 to January 2025 uncovered approximately 150 S3 buckets previously owned by prominent corporations and governmental entities that were deleted but still referenced in outdated DNS records. These defunct buckets attracted over 8 million requests seeking critical resources like container images and SSLVPN server configurations, illustrating the tangible risks associated with Dangling DNS attacks.
The implications of subdomain takeovers extend beyond superficial website defacement or credential theft to potentially include injecting malicious code into supply chains. Organizations rely on subdomains to distribute software updates and other vital assets, making them prime targets for attackers seeking to introduce malware into these pipelines, leading to severe consequences like remote code execution and persistent backdoors.
Corroborating these concerns, cybersecurity firm SentinelOne identified over 1,250 instances of subdomain takeover risks arising from decommissioned cloud resources in the past year. They stress the importance of implementing robust security practices throughout the software development lifecycle, with a particular focus on runtime security when engaging third-party services.
This evolving threat landscape underscores the critical need for meticulous DNS management practices within organizations. It is imperative for businesses to actively monitor and securely decommission subdomains, ensuring that all associated DNS records are removed to prevent exploitation by malicious actors.
As the cybersecurity landscape continues to evolve, maintaining proactive security measures through diligent monitoring and timely updates to cloud and DNS configurations is paramount to safeguarding against sophisticated attacks like Dangling DNS exploits. By staying informed and implementing robust security protocols, organizations can fortify their defenses and mitigate the risks posed by these prevalent cyber threats.