How do overcockers find out about corrected hosts?

Question

Ad blocking

I went to overclockers.ru today and saw the following message:
"Dear visitor!
We have determined that you are using an ad removal system - Adblock, AdGuard or some other (including the corrected hosts file). "
I am most interested in the corrected hosts: how do they find out about this or is it just an addition to the message, and in fact there is no way to do any verification?

Answer 1

1. From the page we send a request to ad.taburetka.com
2. We do not see the request in the logs of the stool
3. Conclusion - the user in the hosts says:
127.0.0.1 ad.taburetka.com

Answer 2

They also wrote with a mistake, correctly “corrected”.
But like this. From the page code.

var script = document.createElement('script');
script.onerror = function(){
   // тут пишем сообщение об ошибке
}
script.src = "https://c.amazon-adsystem.com/aax2/amzn_ads.js";
document.body.appendChild(script);

That is, everything is simple: if an error occurred while calling the advertisement, we display a message.
Here are creepy bastards, another site written entirely in JS and outputting nothing when there is none.
Yes, and a typo you have to match this bastard: "overcockers".