Why does Norton Security detect PLEX activity virus?

What is Plex doing here that activated a security warning?

It’s a false alarm.
The domain name xxx.xxx.xxx.xxx.abcdefghijklmnopqrstuvwxyz0123456789.plex.direct is used by Plex to test for a certain feature of your network’s DNS resolver. To then work around it, when detected.

My private opinion: anything with “Norton” in the name stopped being useful shortly after Peter Norton sold his business back in the 1990s.

Thanks for the explanation. I’ll mark this one solved.

Ya, Norton is a poor virus tool. I consider it more like bloatware or spamware.