Only thing I can think of is verification on the opposing client the information isn't bogus and even that can easily be falsely reported to get the other person thrown out
Depends how much it matters, for instance, online versus it's a nightmare scenario, but if it's a game like Payday in the way it's set-up you don't need to care about cheating. Cheaters gonna cheat, just don't play with them if that's not your thing.
Mind you, cheating was rampant in Payday 2, I personally cheated but only in the skillpoints, allowing me to easily switch between classes after what was required (opposed to being stuck being able to play one role and that's that unless you respec constantly). Playing mostly with a single friend, it actually improved my gaming experience.
Without any infrastructure you're stuck with peer-to-peer matchmaking and direct IP joining, which again isn't that bad if it's a coop game, people adapt to that if the game is good, but effectively the worst thing available for online versus, and you'll need to get your game on Steam or something to avoid hosting files yourself. Well, if you get it on Steam, you can use them as the matchmaking service, which would be a severe improvement.