SSDP

SSDP is the discovery protocol behind UPnP, letting devices announce themselves and find services on a local network over UDP port 1900. Millions of devices answer SSDP queries from the internet when they should not, and because responses are much larger than requests, attackers abuse them for reflected DDoS amplification. Blocking UDP 1900 at the network edge removes both the amplification risk and unwanted device exposure.