Subdomain Monitoring
An inventory of your subdomains — and the ones someone else could take over.
The subdomain monitor finds every hostname under your domain that ever had a certificate, checks each one in DNS and compares with the previous run.
What it detects
- New subdomains you didn't know about
- Dangling CNAMEs — names pointing at something that no longer exists, the classic takeover
- Subdomains that no longer exist in DNS
How you're alerted
- “New Subdomain Detected” and “Dangling Subdomain CNAME Detected” (critical) fire on their own.
Notifications go to any of 8 channels — see notifications.
- Runs from
- MonSPHERE's own workers — no region to pick
- First check
- Records a baseline — nothing is flagged until something changes
- Interval
- At most every 6 hours
- Dashboard
- Subdomains by status (live, no DNS, dangling CNAME, new), their trend, takeover risk, the full list with addresses and CNAMEs, and run history
- Available on
- Professional · Enterprise and Custom on request
More in Security & Domains
View categorySSL Monitoring
Certificate expiry alerts before anything breaks.
WHOIS Monitoring
Track a domain's own registration expiry and catch an unexpected ownership transfer — independent of its SSL certificate.
Certificate Transparency Log Monitoring
Get notified the moment a new certificate is issued for your domain or a subdomain — catches unauthorized issuance and shadow IT early.
Typosquatting Monitoring
Find registered lookalikes of your domain — typos, homoglyphs, IDN homographs, other TLDs, "brand-login" names — and get alerted when a new one appears.
Port Discovery
Full-range TCP port scan of a host you own to flag any port that's open now but wasn't before — an early warning for an accidentally-exposed service.
DNS Blacklist Monitoring
Check whether an IP (or a hostname's IP) is listed on spam blacklists — catch a reputation problem before it blocks your mail.
Email Authentication
Watch a domain's SPF, DKIM and DMARC records for the silent misconfiguration that tanks deliverability.
Cookie Monitoring
Track a page's cookies for unexpected additions, removals, or security-attribute changes — Secure, HttpOnly, and SameSite, not just whether a cookie is still there.
Third-Party Script Integrity
Get alerted when a third-party script your page loads changes — an early warning for supply-chain and card-skimming attacks.
Start monitoring everything in minutes
Create a free account, add your first check and get alerted the moment something breaks — no credit card required.