I've had a few people say they got the cracked version before buying the game and some of them felt bad so they bought the game for others but that's no excuse. They shouldn't be able to crack the game and connect to multiplayer servers via direct IP.
So here is my idea...
Multiplayer servers will have to check with factorio servers if the user that connects has a uuid ( Unique User Identification ) number and it will check when the account was made and if the user was paid or not. Or maybe not even that. It would just check if the user is real. So the server will reject connections that have a invalid session ID or users who don't have a valid account. Meaning all cracked clients shouldn't be able to join.
This would help a lot to prevent people getting the game for free.
( My knowledge of this is based off Minecraft's system )
( To prove I own the game ) :/
![Image](https://img.hypergaming.co.uk/screenshots/QldK0G13.png)