DNS leak
From Wikipedia, the free encyclopedia
A DNS leak is a security flaw that allows DNS requests to be revealed to internet service provider (ISP) DNS servers, despite the use of a VPN service to attempt to conceal them.[1] The vulnerability allows an ISP, as well as any on-path eavesdroppers, to see what websites a user is visiting.
This only occurs with certain types of VPNs, e.g. "split-tunnel" VPNs, where traffic can still be sent over the local network interface even when the VPN is active.