What is Subdomain takeover?
Subdomain takeover happens when a DNS record for one of your subdomains still points at an external service that you no longer use, and someone else can claim that service name and serve content as your subdomain.
Why businesses care
Attackers can host phishing pages or steal cookies on what looks like your genuine domain.
Example
shop.example.com CNAME example.shopprovider.net, after the provider account was closed.How to check
List your subdomains and look for CNAMEs whose targets no longer resolve or show “not found” pages.
How to fix
Delete DNS records for services you no longer use before cancelling the service.
Common mistakes
- Cancelling a service without removing its DNS record
- No inventory of subdomains
Check it with Domain Security Checker
Review your domain’s DNS health: nameserver redundancy, CAA, DNSSEC and dangling CNAME indicators. Free domain security check.
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