Core network servicesUDP 1900 Cleartext by default
Port 1900: SSDP
Simple Service Discovery Protocol (UPnP)
Device discovery for Universal Plug and Play on home and office networks.
How attackers abuse it
- Reflection DDoS from internet-exposed devices.
- UPnP letting internal devices open firewall ports on their own.
How to defend it
- Disable UPnP on routers; block 1900 at the edge.
Exam tip
UPnP on an internet router is a convenience feature that quietly bypasses your firewall policy.