It's most time leak by hackers or by ex workers which are pissed for being fired. But there are as well tools to sniff the package transfer. Means you play the game fully, visit all angle for the game, sniff and copy the data while its transferred and then try to build something out of it. That's the very hard way. The easy way is to search for a leak which is most time done already by others. In any case, PC and mobile is not very different. Both needs a client and a server copy.
