there's cheaters in every human activity, more so when you throw money in the mix. about a year ago a CSGO pro - someone who actually gets paid to play - was caught cheating .. at a LAN event. (he had his hack stored on his cloud profile)
this in turn got several of the highest-ranking world players to be outed as cheaters, because, again, MONEY.
in the world of eSports, Valve is actually considered one of the best at dealing with hackers; their VAC system is one of the few effective ones, they are brutal in their punishment, and they use a "sheriff" system where some responsible players have temporary ban powers.
the problem is that hacks are not easy to fight. client-server communication is too easy to spoof, and the combination of possible gain + free hacks means your game will be infested no matter what - it's like trying to live your life without ever catching the herpes virus, or the flu.
play with friends only .. or play pickups .. or better yet, branch out. quake is nearly hacker-free (as it would be super-obvious) and the servers are pretty much godlike-grade. same goes for UT and Reflex. If you like the CS recoil system, then Ghost In The Shell - First Assault could be a viable alternative, and since it's a new engine, there's no hackers as yet.