How DNS security works
Nearly every connection begins with a DNS lookup, which makes DNS a useful control point. Filtering services compare requested domains with threat intelligence and block known malicious, phishing, or newly registered suspicious sites before a connection is made.
DNSSEC adds digital signatures so resolvers can verify that answers are authentic and unaltered, defending against spoofing and cache poisoning. Monitoring DNS logs can reveal malware beaconing and data exfiltration through DNS tunnelling. Encrypted DNS, such as DNS over HTTPS, protects queries in transit but needs governance.
Why it matters for Canadian organizations
Attackers rely on DNS for phishing sites, malware delivery, and command-and-control, so blocking at this layer stops many threats cheaply and early. The Canadian Centre for Cyber Security offers a protective DNS service for eligible public sector organizations, reflecting its value.
Domain hijacking and DNS misconfiguration can also take websites and email offline or redirect customers to fraudulent sites. Canadian organizations using .ca domains work through CIRA, and should secure registrar accounts with strong authentication. Reliable DNS is part of overall availability and brand protection.
How to implement it
Use a protective DNS or DNS filtering service for all users and devices, including remote workers. Log queries centrally and alert on unusual patterns, newly registered domains, and high volumes of failed lookups.
Sign your own zones with DNSSEC where supported, lock your domains at the registrar, and enable multi-factor authentication on registrar and DNS provider accounts. Deploy SPF, DKIM, and DMARC records to reduce email spoofing of your domain, and review DNS records regularly for stale entries that could be abused.
Frequently asked questions
What is DNSSEC?
DNSSEC is a set of extensions that adds cryptographic signatures to DNS data so resolvers can confirm responses are authentic. It prevents spoofing and cache poisoning but does not encrypt queries or block malicious sites. Many organizations deploy it on their own authoritative zones to protect their domains.
Does DNS filtering replace a firewall?
No. DNS filtering blocks malicious domains before connections form, but it does not inspect all traffic or stop direct IP connections. It works best as one layer alongside firewalls, endpoint protection, and email security. DNS filtering is best deployed together with those other controls.
What is DNS tunnelling?
DNS tunnelling hides data inside DNS queries and responses so attackers can send commands or steal data past controls that allow DNS traffic. Monitoring query size, frequency, and unusual domains helps detect it. Large or frequent queries to odd domains are typical warning signs.
Related service: Managed security services