Public Wi-Fi Client Isolation Is Weaker Than Most Users Assume

Client isolation, a common Wi-Fi security feature that blocks direct device-to-device communication, is neither mandatory nor universally enabled on public networks. Even when active, researchers at the SANS Institute have documented techniques — including abusing shared broadcast traffic and spoofing MAC or IP addresses — that can bypass it without breaking encryption. Beyond isolation gaps, devices routinely broadcast identifying information via protocols like mDNS and Bonjour, exposing device names and enabled services to anyone on the same network. Apple's AirDrop was separately found by TU Darmstadt researchers in 2019 to leak hashed contact details that can be brute-forced, a flaw not fully resolved as of writing. Security experts recommend disabling unused sharing features, verifying firewall settings manually, and relying on always-on protections rather than per-network checks.