DNS Monitoring: Catch Unauthorized Changes Before They Cause Outages

DNS is the foundation of your web presence. When DNS records change unexpectedly — whether from a misconfiguration, an expired domain, or a malicious hijack — the results can be catastrophic and difficult to diagnose.

Why DNS Changes Are Dangerous

Unlike a server crash that shows a clear error page, DNS issues are invisible and confusing:

• Your site works for you but not for others — DNS caching means some users see old records while others get the new (broken) ones.
• Email stops working silently — A changed MX record means emails to your domain bounce or get delivered to the wrong server.
• SSL breaks — If your A record points to a new IP, your SSL certificate may not cover it.
• Recovery is slow — DNS changes propagate over hours or days due to TTL values and caching.

Common DNS Threats

Unauthorized Changes

An attacker who gains access to your DNS provider can redirect your entire domain to a malicious server. This is called DNS hijacking and it's more common than you'd think.

Domain Expiry

If your domain registration expires, anyone can register it. Your entire web presence — site, email, everything — is gone.

Registrar Issues

Registrar outages, account lockouts, or policy changes can affect your DNS without any action on your part.

Accidental Misconfiguration

A team member updating DNS records for one service accidentally breaks another. Without monitoring, these mistakes can go unnoticed for days.

What to Monitor

Comprehensive DNS monitoring should track:

• A / AAAA records — Where your domain points. Any change means traffic goes elsewhere.
• MX records — Email routing. A change here can silently redirect your email.
• NS records — Your nameservers. If these change, an attacker controls everything.
• TXT records — SPF, DKIM, and DMARC records for email authentication.
• CNAME records — Alias records for subdomains.
• CAA records — Which certificate authorities can issue certs for your domain.
• SOA records — Zone authority information, including serial numbers.

Setting Up DNS Monitoring

With WebMon, DNS monitoring is straightforward:

1. Create a new monitor and select the DNS type
2. Enter your domain name
3. Choose the record type to monitor (A, MX, NS, etc.)
4. Optionally set an expected value to match against
5. Select which DNS servers to query (Cloudflare, Google, Quad9, and more)

WebMon queries your DNS records on every check cycle and alerts you if:

• The record value changes from what's expected
• The record disappears entirely
• The DNS query fails or times out

Multiple DNS Server Queries

WebMon can query the same record across multiple DNS providers simultaneously. This is valuable because:

• It detects propagation issues (your record is correct on one server but not another)
• It catches DNS provider-specific problems
• It verifies that all major resolvers return consistent results

Supported DNS servers include Cloudflare (1.1.1.1), Google (8.8.8.8), Quad9, OpenDNS, AdGuard, and more.

Best Practices

• Monitor NS records for all critical domains — This is the most important record type; if nameservers change, everything is compromised.
• Set expected values — Don't just monitor for availability; verify that records contain the correct values.
• Monitor MX records — Email security starts with ensuring MX records haven't been tampered with.
• Check CAA records — These prevent unauthorized certificate issuance for your domain.
• Use multiple DNS servers — Query from at least 2-3 different resolvers to catch propagation issues.

DNS monitoring is one of the most overlooked aspects of website security. A few minutes of setup can save you from days of troubleshooting and potential data loss. Add DNS monitors for your critical domains today.