How closely does Valve monitor well known cheating websites and how well does it sniff out cheaters?

So I was perusing "top" posts in the CS GO sub and it lead me to a certain cheating forum...it was startling that the CS:GO section of the site had over 150k views.

I JUST started playing CS (less than 30 hours) and am still learning...so I hate having the nagging feeling that people have an unfair edge over me while I'm trying to measure myself against them.

I have suspected a bunch of people in pub matches with shady play...now I'm trying to gauge how many people are cheating. Honestly, I'm a little discouraged. I used to play SoF2 competitively and the Punkbuster system sucked ass.

How well has Valves anti-cheat system worked to find the cheaters and how well does it find some of those cheats? It seems like a lot of them are outside the game...do they ever get detected?