Quad9 is a free service that replaces your default ISP or enterprise Domain Name Server (DNS) configuration. When your computer performs any Internet transaction that uses the DNS (and most transactions do), Quad9 blocks lookups of malicious host names from an up-to-the-minute list of threats. This blocking action protects your computer, mobile device, or IoT systems against a wide range of threats such as malware, phishing, spyware, and botnets, and it can improve performance in addition to guaranteeing privacy. The Quad9 DNS service is operated by the Swiss-based Quad9 Foundation, whose mission is to provide a safer and more robust Internet for everyone.