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So, I am currently building a multiplayer game, and havent run into any hackers yet, but need to know what to do in order to protect against them in the future. Basically, what could potential hackers change in the javascript source? I know people can right click and modify the source code then run it again locally, but that wont be connected the server so i dont care, but other than that i dont know what to look out for. Inventory data, locations of players etc are all stored on the server and I dont save anything on the players local side, is that all i really need to do in order to prevent cheaters from some how modifying something important that gives them an advantage, such as speed hacking or changing what they have in there inventory. Is saving important data on the server all i really have to do? This might be a little confusing what im asking but im kinda in a rush and wanted to post this before I left. Thanks for the help in advanced.