What is UPnP
UPnP (stands for Universal Plug and Play) is a set of network protocols. UPnP is designed to automatically configure network devices. Simply put UPnP automatically forwards a port if the connection was initiated from the local network. It trusts the LAN outgoing requests by default.
Vulnerability in UPnP implementation
Some models of routers have bad implementation of UPnP. This makes the router vulnerable. Such vulnerability can help hackers change DNS setting on router. After that all devices on a LAN can be routed to a phishing site, a ransom demanding page or even encrypt your files.
The malware located on any device on the LAN can initiate the outgoing connection to its server. If the router has UPnP enabled it means that it would trust any outgoing connections and allow to forward a port. Thus the malware would be able to bypass the router, establish a connection with malicious server and as a result provide a permanent access to your computer.
How to disable UPnP on Router
Go to Forwarding ? UPnP and press Disable.
(If UPnP is already off the button would be named “Enabled” and you would see notification “Current status: Disabled”)
Go to Advanced ? Advanced Network.
Unset the checkbox Enable UPnP.
Press Save Settings: