What is QUAD9 Technology

Quad9 is a free public DNS resolver that protects users from malware, spyware, botnets, and other security threats. Operated by the Swiss-based non-profit Quad9 Foundation, it provides enhanced security and privacy by blocking access to malicious websites while maintaining GDPR compliance through strict data protection policies.

Unlike traditional DNS services that may collect and monetize user data, Quad9 does not store or log users' IP addresses. It blocks malicious domains using real-time threat intelligence from cybersecurity experts and companies, preventing devices from connecting to known dangerous websites.

How Quad9 Works

Quad9 operates as a recursive DNS resolver, meaning it processes DNS queries by contacting other DNS servers on behalf of clients and returns complete responses. When a user requests a domain name, Quad9 first checks if the domain appears on its threat intelligence feeds. If the domain is flagged as malicious, Quad9 blocks the request and returns an NXDOMAIN response, preventing the connection.

Quad9 DNS Configuration

Users can configure their devices to use Quad9 by setting the DNS server addresses. Quad9 offers both secure and unsecured options:

Secure Configuration (Recommended)

Unsecured Configuration

Security Features

Quad9 implements multiple security technologies:

• DNSSEC Validation Cryptographically verifies DNS responses to prevent DNS spoofing and cache poisoning attacks.

• DNS over TLS (DoT) Encrypts DNS queries using TLS on port 853 to prevent eavesdropping.

• DNS over HTTPS (DoH) Provides encrypted DNS resolution over HTTPS for additional privacy.

• DNSCrypt Encrypts communication between DNS clients and resolvers to prevent tampering.

Privacy Protection

Quad9 maintains strict privacy standards by not logging user IP addresses, which it treats as Personally Identifiable Information (PII). The service temporarily stores "reply to IP addresses" in RAM but destroys them immediately after sending responses. It only collects aggregate statistics about query types, response codes, and transport protocols without correlating data to individual users.

Advantages

• Free service No cost or additional software/hardware required

• High availability 99.999% uptime with global redundancy

• Real-time protection Continuously updated threat intelligence

• GDPR compliant Strict data protection and privacy policies

Conclusion

Quad9 provides robust DNS security by blocking malicious domains while protecting user privacy through its no-logging policy. As a free, globally available service with high uptime and multiple security protocols, it offers an effective solution for enhancing internet safety without compromising performance or privacy.