Quad9 is largest of the three global public recursive DNS resolvers which protect users from malware and phishing, and is notable for consistently being found to be by far the most effective (97%) at doing so in independent evaluations, blocking more than 100 million malware infections and phishing attacks per day. It was the first to use standards-based strong cryptography to protect the privacy of its users' communication, and the first to use DNSSEC cryptographic validation to protect users from domain name hijacking. Quad9 protects users' privacy by not retaining or processing the IP address of its users, and is consequently GDPR-compliant.