Hmmmm.... You love Counter-Strike, but you don't want to pay for it. Normally when this happens to me, I just go out and google and crack and or registry key for the product.
Vavle is pretty smart in validating the CD Key EVERY time you log on as well as when you install it. They Validate it with their servers, which are obviously at a remote location. What you want to do is either send Valve false data, which they will discover or not send them data at all, which will cause them to shutdown your Steam Client.
I'd personally buy a CD Key. It is what 50 dollars now, probably less because of HL2, but if you are poor or don't want to pay, you can try to spoof your login with valve or something.
I personally have my own account and don't really have a need to "hack" valve's log in process, so I have no information about this. If you love Counter-Strike, then why not contribute to the people who made it, so that they can spend that ***** on developing an even better more inprovded version of Counter-Strike. This way they will have ***** for R 'n D and will be able to make your favorite game that you love even more fun.
People confuse me. They steal from the things that they love, which eventually ends up killing what they stole from.
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Translation = "In electronic warfare, the winner is the one who built the EMP."