Glossary · Circumvention

DNS filtering

Also calleddns blockdns censorship

Definition

DNS filtering blocks websites by making the DNS resolver return a fake response — the cheapest and most common first-line censorship tool.

Explanation

In depth

When your device asks the DNS resolver for a domain's IP address and the resolver is under filtering policy, it returns NXDOMAIN (domain does not exist), a blockpage server IP, or nothing at all. Your device cannot reach the site because it has no address to connect to. Switching your DNS to a public resolver (1.1.1.1, 8.8.8.8) defeats DNS filtering — provided the network does not also block outbound port 53 or force redirect DNS queries. Enterprise networks often force DNS through their own resolver. DNS filtering does nothing against IP-level or DPI-level filtering — for those, a proxy or VPN is required.

Related terms

IP blockingIP blocking drops packets destined for specific IP addresses at the network firewall level — bypasses DNS entirely.DPI (Deep Packet Inspection)Deep packet inspection reads not just packet headers but payload contents to identify and filter specific protocols, applications, or destinations.DNSDNS is the internet's address book — it translates human-readable domain names like anyproxy.site into IP addresses computers use to connect.DNS-over-HTTPSDNS-over-HTTPS (DoH) sends DNS queries wrapped in HTTPS — hiding domain lookups from your ISP and network operator.

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