mDNS
mDNS (Multicast DNS) lets devices on a local network resolve each other's names, typically ending in .local, without a central DNS server. A device announces its own name over multicast UDP on port 5353, and any other device on the same network segment can ask "who has this name" and get a direct reply, which is how Apple's Bonjour/AirPrint and many smart-home and IoT devices find printers, speakers, and cameras nearby. Because mDNS queries and replies are multicast and unauthenticated, the main risk is scope: it is meant to stay inside a single local network, but misconfigured routers or VPNs that bridge mDNS across network boundaries can leak device names and services to networks that shouldn't see them, and devices that answer mDNS queries from the public internet become a reflection target for abuse.
By AdminKit team, Netbase JSC · Updated