Aside from copyright issues, one of the reasons most companies don’t like fan-run servers for their games is because they can’t control the code that is being executed on these servers. From a security standpoint, it means that developers cannot guarantee that it is 100% safe for gamers. That is bad news.
If you like playing on fan-run servers, then you might want to check out this leak, especially if you play games like Valve’s Team Fortress 2 or Counter-Strike: Global Offensive. Source code for both games have been leaked. So some fan servers are being taken offline until they can decide if these leaks could compromise the security of players on these servers.
These files appear to be several years old, so unless the server you’re playing on is running a very old version of either game, there is a chance that the leak might not have any impact on your security at all. Valve has confirmed the leak and has suggested that there isn’t anything to be worried about, but they will be investigating it.
A statement issued by the company said, “We have reviewed the leaked code and believe it to be a reposting of a limited CS:GO engine code depot released to partners in late 2017, and originally leaked in 2018. From this review, we have not found any reason for players to be alarmed or avoid the current builds (as always, playing on the official servers is recommended for greatest security). We will continue to investigate the situation and will update news outlets and players if we find anything to prove otherwise.”