DNS Leak

What Causes a DNS Leak

When you connect through a VPNVirtual Private Network. A technology that creates an encrypted tunnel between a device and a remote server, protecting data in transit and masking the user's real IP address. Used for privacy, security, and accessing restricted networks., your DNS queries should travel through the encrypted VPN TunnelAn encrypted, encapsulated connection between two endpoints through which all tunneled data passes securely across an untrusted network like the public internet. and be resolved by the VPN provider's DNS ResolverA server that receives DNS queries from clients and resolves domain names by querying the DNS hierarchy on their behalf. Public resolvers like 1.1.1.1 (Cloudflare) and 8.8.8.8 (Google) are widely used alternatives to ISP resolvers.. A DNS leak occurs when those queries bypass the tunnel and go directly to your ISPInternet Service Provider. A company that provides internet access to consumers and businesses, assigning public IP addresses and routing traffic to the wider internet. Examples include Comcast, AT&T, and SK Broadband.'s resolver instead. This reveals which domains you are visiting even though your traffic is otherwise encrypted and your Public IP AddressA globally unique IP address assigned by an ISP that is routable on the public internet. Every device directly accessible from the internet must have a public IP address. is hidden.

Common Causes

DNS leaks typically occur due to operating system misconfigurations, DHCPDynamic Host Configuration Protocol. A network protocol that automatically assigns IP addresses, subnet masks, gateways, and DNS servers to devices when they join a network.-assigned DNS servers that take precedence over VPN settings, or IPv6 connectivity that is not routed through the tunnel (an IPv6 leak). Windows systems are particularly prone because they use a feature called Smart Multi-Homed Name Resolution that queries multiple resolvers simultaneously.

Detection and Prevention

Use DNS Leak Test to check whether your queries are leaking outside the VPN. If a leak is detected, the fix usually involves forcing all DNS traffic through the VPN's resolver, disabling IPv6 if the VPN does not support it, or enabling the VPN client's built-in DNS leak protection setting. Choosing a VPN that supports WireGuardA modern, lightweight VPN protocol that uses state-of-the-art cryptography (ChaCha20, Curve25519) with a minimal codebase (~4,000 lines). Designed for simplicity, high performance, and low latency compared to OpenVPN and IPSec. or OpenVPNAn open-source VPN protocol that uses SSL/TLS for key exchange and can operate over UDP or TCP. Known for its flexibility, strong security, and wide platform support, though slower than WireGuard. with kill-switch functionality also reduces the risk of leaks during connection drops.