subdomain takeover

What is Subdomain Takeover?

A subdomain takeover occurs when a subdomain (e.g., blog.example.com) points to an external service that has been removed or is no longer in use, but the DNS record still exists. Attackers can claim the abandoned resource and host malicious content, leading to phishing, malware distribution, or reputational damage.

How Subdomain Takeovers Work

1. An organization creates a subdomain.
2. The service is later removed, but the DNS record pointing to it remains.
3. An attacker registers an account with that service and claims the subdomain, effectively taking it over.

Why Subdomain Takeover is Dangerous

• Attackers can host phishing pages that trick users into entering sensitive information
• Malicious files or malware can be distributed from a trusted-looking domain
• Organizations risk reputational damage and loss of customer trust

How to Prevent Subdomain Takeovers

• Regularly audit and remove unused DNS records
• Reconfigure DNS entries to point to valid services if still needed
• Use asset discovery to detect forgotten subdomains

How Intruder Helps

Intruder’s automated asset discovery finds forgotten subdomains so you can remove or secure them before attackers do, and our bug hunting team can check for subdomain takeover.

Learn more or book a demo to see Intruder’s asset discovery in action.