For those of you that might not be aware, in Korea your Battle.Net account is tied to your Social Security Number, so the punishment for being banned due to cheating is much more severe than in the West where you can just purchase another copy. Unfortunately, this whole system can currently be circumvented by creating free accounts on the NA or EU regions - a process that doesn't require any identifying information. These accounts can then be used in PC Bangs (Korea's version of an Internet cafe) to play Overwatch for a fairly minor fee, essentially giving you access to an infinite amount of accounts with no actual risk involved whatsoever.
As you might imagine, when there is no oversight or any real punishment the temptation to start cheating becomes far too much for some people to resist. And after many months of complete silence from Blizzard the situation has become somewhat unbearable due to the amount of cheaters in North American and Korean servers. Thankfully, that is soon going to change, as according to the most recent Overwatch blog the developers are going to start requiring foreign accounts to purchase the game itself before playing it in a PC Bang.
If you're interested in a summary of the whole post you'll find lomotos10's brief translation over at Reddit. But long story short, you can expect to see a drastic decrease in the number of cheaters from February 17th and onward, once the system finally goes live. This will initially only apply to Overwatch, but Diablo 3 and Starcraft 2 will soon follow suit as well. While all of this is probably not going to stop 'hackers', its still a damn good first step at making sure that cheating is as unattractive as possible.