Moderation!

Hi  greaver.

this is the offtopic room, so this is the place for anything not! about games. Since yours is a game related question this topic more propperly belongs in General game discussion, so I'll move it.

As to your question, perhaps if you give us a bit more of an idea?
Firstly which online games exactly are you talking about when you say "online games? there are lots of different online games and some of  connect to opponents in different ways, EG some have servers, some you have to host games, some are muds etc.

Secondly, what computer are you on? Many networks at schools and universities have additional security that blocks certain things from running, which is very annoying indeed.

Then, you mention "turning off" windows defender, but windows defender has lots of different bits. In particular here I'm wondering about your firewall, since usually in windows 10 when you launch any new online application, you have to alt tab out of it to the window and manually allow it through the firewall.
This is fine once you've done it,but needs doing first time around just to make sure your connection is okay.

The other thing about windows 10 is that your general security settings will probably dictate how much of windows defender turns itself back on even if you turn it off, and I'd be interested to know what your user account control was set to.

Maybe they're reacting to the presence of cheat engine, maybe its some other thing, who knows. It's kind of hard to say. I don't believe its anti-virus related since if it were, the program would never have been allowed to start in the first place.