Free security tool
Find subdomains that still point to a cloud service you no longer use, before someone else claims the name and serves their content on your domain.
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An alias is reported only when its target is confirmed not to exist, or when the service's own "no such site" page is seen. A lookup that times out is shown as not checked, never as vulnerable. Services covered: Microsoft Azure, AWS Elastic Beanstalk, GitHub Pages, Heroku, Amazon S3, Shopify, Fastly, Pantheon, Tumblr, Ghost, Surge.sh, Bitbucket, Help Scout Docs, ReadMe, WordPress.com, Zendesk.
To see every record on one name, use the DNS Lookup; for a broader one-time review, the Domain Health Check.
A subdomain points (with a CNAME) to a service such as GitHub Pages, Heroku or Azure, and the account or app at that service is deleted while the DNS record stays. Anyone can then create an app with the same name and serve their own content on your subdomain, including phishing pages and cookie theft.
Two ways. If the alias target no longer exists (NXDOMAIN) and the service lets anyone register that name, it is reported as likely claimable. If the target exists, CloudSpex loads the page once and looks for the service's own "no such site" message. A match is strong evidence, not proof; CloudSpex never tries to claim anything.
45 common names (www, api, blog, shop, status, docs and others), plus a random name to detect a wildcard record. Subdomains with other names are not discovered; your DNS zone is the complete list.
When the resolver or the page does not answer, the result is not counted as safe or as vulnerable. Run the check again later.
Delete the CNAME record for the subdomain at your DNS provider, or re-create the app or site at the service with the same name. Deleting is the safer default when the service is no longer used.
Add your domain to CloudSpex to have its subdomains checked on a schedule and be alerted when one starts dangling.
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