Domain Monitoring Coverage Calculator

Example Data Table

Formula Used

• Basic Coverage (%) = Monitored Domains ÷ Total Domains × 100
• Weighted Coverage (%) = (CriticalMonitored×Wc + StandardMonitored×Ws) ÷ (CriticalTotal×Wc + StandardTotal×Ws) × 100
• Methods Score (%) = Selected Method Weights ÷ Total Method Weights × 100
• Overall Coverage Index (%) = 0.45×Basic + 0.25×Weighted + 0.15×Methods + 0.10×Frequency + 0.05×Alerts + DepthBonus

How to Use This Calculator

1. Enter domain counts, or paste your scope and monitored domain lists.
2. Paste critical domains you cannot afford to miss.
3. Select detection methods used by your monitoring stack.
4. Choose scan frequency and alert channels used for notifications.
5. Click Calculate Coverage to view results above the form.
6. Export a CSV or PDF report for reviews and audits.

Interpretation Tips

Asset inventory defines the denominator

A reliable coverage calculation starts with a defensible domain inventory. Treat “total domains” as the authoritative scope: corporate domains, delegated brands, parked defensive registrations, and third‑party domains you control. Keep ownership, registrar, DNS provider, and business function fields so exceptions are explainable during audits. If you paste scope lists, de‑duplicate entries and normalize hosts, because duplicates inflate the denominator and hide real gaps. Record renewal dates and redirect destinations too.

Criticality weighting improves risk alignment

Not every domain carries the same consequence. Weighting critical domains focuses monitoring on assets that enable authentication, payments, customer portals, and email delivery. Use a higher critical weight when compromise creates direct fraud, credential theft, or brand damage. Maintain a short critical list that is reviewed quarterly, and validate that critical domains are actually monitored rather than estimated, using explicit monitored lists where possible. Include domain age and exposure history in reviews.

Signal depth reduces detection latency

Coverage is more than “is it watched”; it is “what signals are watched.” Combine DNS change detection, certificate transparency watching, HTTP checks, and subdomain discovery to capture different attacker behaviors. Add typosquat and brand alerting when abuse targets customers outside your owned infrastructure. The methods score in the calculator rewards breadth of signals, because deeper telemetry reduces time to confirm malicious activity. Log method coverage per domain group to avoid size assumptions.

Cadence and alerting drive response outcomes

Scan frequency and alert delivery determine whether coverage becomes action. Faster cadence improves detection of short‑lived phishing infrastructure and rapid DNS or certificate changes. Pair at least two alert channels, such as ticketing plus chat, to reduce missed notifications during outages or inbox overload. When frequency is constrained, compensate with stronger methods and tighter critical coverage, then document the residual risk for leadership. Test escalation paths quarterly with exercises and metrics.

Using the index for governance and budgeting

Use the overall coverage index to track program maturity, not to claim absolute safety. Trend the index monthly, annotate major inventory changes, and set a target threshold aligned to your risk appetite. Where gaps persist, quantify the uncovered count and prioritize onboarding by criticality, business impact, and exposure estimate. Export CSV and PDF reports for audits, vendor reviews, and budget justifications. Tie improvements to SLA goals, incident rates, and registrar lock adoption.

FAQs

What does Basic Coverage measure?

It measures monitoring breadth: monitored domains divided by total in-scope domains. It does not reflect method depth, alerting reliability, or scan cadence, which are incorporated into the overall coverage index.

When should I paste domain lists instead of counts?

Use lists when you can export inventory from registrars, DNS, or CMDBs. The calculator normalizes and de-duplicates domains, giving more accurate totals and better critical coverage calculation than manual counts.

How do I set Critical Weight?

Start with 3 for domains tied to authentication, payments, and email. Increase the weight if compromise has direct financial impact, strict regulatory requirements, or severe brand risk. Keep weights consistent so trends remain comparable.

Which monitoring methods should be prioritized first?

DNS change monitoring and certificate transparency watching catch many hijack and phishing setups early. Add HTTP checks for defacement and header changes, then subdomain discovery and typosquat detection to reduce blind spots around shadow assets.

What scan frequency is reasonable for most teams?

Daily is a common baseline for broad coverage. Hourly or near-real-time is better for critical domains and high-risk brands. If you scan weekly, strengthen methods and alert channels and document the increased detection window.

How should I interpret the Exposure Estimate?

It is a heuristic planning indicator based on coverage gaps, method depth, and cadence. Treat it as directional: use it to prioritize onboarding and controls, then validate with incident history, threat intel, and authoritative asset inventory.