I'm continuing to receive these warning messages when the extender is switched on. I'd really appreciate some help with this!

 Hi @DavidMW,

Could you provide a screenshot of the warning? If you connect the PC directly to the router's Wi-Fi, does the same happen?

Please let me know the operating system and model of the PC. Also, what is the model of the router?

Many thanks Joseph. Inevitably, the fault doesn't happen continually, and now I want it show up, so far it hasn't! I'm all set to get a screenshoot as soon as it does.

To answer your other queries in the meantime:

The PC (which is not an off-the-shelf model) is running Windows 10, and is already connected to the router via ethernet. The TP extender is of course picking up the WiFi transmission from the router.

The router is a Technicolor DGA0122NLK.
The main purpose of the extender is to enable us to use iPlayer etc on our TV at the far end of the house. It's very successful at this - more so than the Powerline Adaptor we were using previously, and which has just failed.

As mentioned I'm currently only switching on the extender when we need to use the TV on catch-up.

The security software is ESET Smart Security Premium and it's this which has been reporting the malicious traffic (which it has blocked).

These error messages only started appearing after the TP-Link extender had been installed so I naturally assumed this was the source of the problem. however it may turn out that it's not the cause.

I'll open discussion with ESET as well in case they can help.

If it does continue happening I'll send the screen shot as promised.