More security settings
Your devices connect to the internet using a series of virtual ports, with different ports used by different applications and services.
Some are standardised — for example, port 80 provides connections to the web, while port 25 is used by SMTP email servers — but others are allocated on an application-by-application basis (if you want to access your Plex Media Server over the internet, for example, you need to connect through port 32,400).
In the past, you had to manually open ports through your router’s setup utility, but thanks to the arrival of Universal Plug and Play (UPnP), apps can now communicate effortlessly with your router and open the ports they need in the background. While convenient, this does open your router to potential breaches (malware can open ports to wreak havoc, for instance). You should, at the very least, check periodically to see which apps have access to your router and if you don’t recognise any, disable it immediately to close all ports. You can then investigate the dubious app further using the IP address to target the device it’s originating from before deciding whether or not you should re-enable it.
A better approach — if a bit less convenient — is to manually set up port forwarding yourself. Apps should alert you when this needs to be done, and you can follow the step-by-step guide at the bottom of this page to see what information needs to be set up for each port.
One final thing: check your router’s support website to see if any firmware updates are available for it. These can add more features, but may also contain security fixes. Installing an update usually involves downloading the update file to your PC, then uploading it manually to your router’s configuration utility where it’s then applied. Be sure to back up or record your settings before doing so, in case the update wipes them out.
“You should, at the very least, check periodically to see which apps have access to your router and if you don’t recognise any, disable it immediately to close all ports.”