@Wolf333 there is a MAJOR worry, no security on the computer means that is is possible for 'bad actors/criminals' to take your computer and use it for their benefit at YOUR cost (ie you pay for the internet and electricity and the computer, but they get to use it (and also see all the files photos and documents that are stored in the computer and ANY storage device that gets plugged into it and use them to benefit them against you)
personally, I am suggesting that you get one of the better antivirus programs (there are some free and good antivirus programs (I suggest checking out the independent antivirus testing sites to short list the different antivirus programs))
The built in Windows 10 security is generally considered a fully fledged virus checker these days (far better than it was). A few years back I still had separate AV, but Windows conflicted so badly with it it had to be removed. Many AV applications have caused more problems than they're worth in the past, anyway.
There's also Windows firewall and the firewall on my Virgin ISP router, protecting from intrusions.
If anything, it's probably best to have some kind of browser anti-malware plug-in or app, depending to some extents on your browsing habits. (I use ad blocker, incidentally, which may or may not help against certain malicious pop-ups.)
I've not had any security issues for many years. Then again, I'm a fairly proficient user, and could probably problem shoot an issue if it cropped up. I also don't tend to download any software from 'unofficial' sources any more. So different strokes for different situations.
Anyway, @Wolf333 - if you want to be sure there is a multiplayer deathmatch in progress, you could try joining the TerraTech discord to check at least *some* others are definitely playing. Then let us know if you still have issues.