Subdomain takeover poses a significant security threat in cloud environments. It occurs when a subdomain of a domain (e.g., subdomain.example.com) inadvertently resolves to an external service no longer under the organization’s control. These orphaned subdomains provide attackers with a foothold for deploying malicious activities like phishing, malware distribution, and data exfiltration. This oversight, often unintentional, creates blind spots in security coverage.
Keytos Research reports discovering over 15,000 vulnerable subdomains monthly in Azure, yet only 2% of organizations actively address this problem. Even major entities like Microsoft are not immune; Keytos identified 700+ vulnerable subdomains associated with Microsoft, underscoring that even large organizations face subdomain vulnerabilities.
This article outlines the impact of a sub-domain takeover, provides an example, and provides examples of the process of establishing an IoC/control.