I've seen one hacker. But they don't hide it.
That's because of what their aim is. If you'd be a cheater and would want to play in the ESL, you'd try to cover it up and fail on purpose sometimes, configureing aimbots to not always headshot, so you can keep a good reputation, having 'people look up to you' and most importantly get a sponsor.
Other people just plain suck and get roflstomped by almost everyone and want to be the big fish for once, which is kinda sad, but they wouldn't try to hide it, because that would imply they either needed the skill to that, which they lacked in the first place or would have play mediocre which wouldn't satisfied their urge to be (rather: feel) superior.
Last but not least there's the griefers, just cheating to piss everyone else off because it pleasures them. Of course, to do so they have to exposition their cheating, because otherwise it wouldn't be annoying enough. But eventually this will get old and they'll move on.