DNS Leak
When your device sends domain lookups outside the VPN tunnel, so your ISP can still see every site you visit even though the traffic itself is encrypted.
Full Definition
A DNS leak occurs when a device using a VPN or proxy accidentally sends DNS queries through the system's default DNS resolver (typically your ISP's) instead of routing them through the encrypted tunnel. This exposes your browsing history to your ISP even though your actual HTTP/HTTPS traffic is protected. DNS leaks typically happen due to misconfigured VPN clients, IPv6 traffic bypassing a VPN that only tunnels IPv4, or Windows-specific DNS behaviour. Privacy-conscious proxy setups route all DNS through the proxy server (as SOCKS5 does when using remote DNS resolution) or use a private DNS-over-HTTPS resolver.
