What is happenning behind adsense ?

I use to surf many websites daily through link referral website.

I came accross few sites saying that their adsense account was disabled.

This blog was denied for adsense by google stating several silly reasons such as

1) This blog should be 6 months active
2) Original content etc.

But, I was surprised to see many blogs with several weeks only old have adsense ads.

Few blogs have so called original content as "CLICK HERE TO DOWNLOAD THE SOFTWARE".
(This is the only sentence available in the blog, and others are links to software downloads) running adsense.

OK. Let us not bother about this adsense. When thinking of adsense now, I just remembered my experience.

Actually I wanted to know what is happening behind this adsense (for removal of account) as reported by many blogs /websites.

How do they know that the blog/website owner is purposefully clicking the ads ?

Many think that they track your id with IP address. But this is not correct, as only few has permanent IP address and many have variable IP address (which changes many times a day).

My Guess :

1) Each machine has address called mac address (machine address) which is unique.
2) Whereever you open your gmail, that mac address is stored by google.

So, when any click is received from a website which mac address is same from the machine the click is received, then it can be presumed that the website owner is clicking the ad.

OR

If you click the ad from outside and the mac address of that machine is already stored against your email id, (if you used that computer for gmail earlier) then it will be clear for google that the click is fraud.

I am not computer genius. So, you need not take this valid reason for disabling the adsense account.

This my doubt. That' s all.