Alright, I know absolutely zilch about computer networks and all that, so I'm not going to pretend that I do, but this is how I understand it (correct me if I'm wrong)... When using Game Maker's multiplayer, you're using your own computer as a server, so your clients are sending packets directly to your computer or something. I'm guessing, that's probably the source of the viruses. But chances are, if you make a multiplayer game, you're only going to be sharing it with us, anyways, and not random strangers on the internet, and I doubt any of us are malicious virus brewers in disguise (right? :<). So yeah, I think as long as you keep it with trusted friends only, it should be safe.
But yeah, then again, I did hear that Game Maker's built in multiplayer sucks (for utility reasons, though, not security).






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