Captcha-sourcecenter.com Pop-ups and Ads
Pop-up ads are nearly everywhere. However, there are many shades of pop-ups, with some much less desirable than others. The pop-ups associated with the domain captcha-sourcecenter dot com are of this kind.
If you are seeing a lot of pop-up ads originating from this domain, it is very likely that at some point you agreed to see them, or were at the very least tricked into agreeing to it.
Sites will sometimes display fake messages and warnings. Those may include fake bot check messages, tricking you into allowing push notifications and pop-up ads, while on your screen, the bait text asks you to click a button to confirm you are not a robot. There are many ways you can end up on such a page - through advertising served on free download websites or other web pages that work with dubious ad networks.
The end result is always the same - the user is somehow dragged onto a fake page that tricks them into agreeing to receive push notifications and pop-up advertising. The issue with this is that a lot of the time, the pop-ups served through those pages are also coming from dubious advertising networks and may lead to pages that contain further malware, browser hijackers, and other unwanted software.
All this advertising content generates revenue for the operators of the ad networks while the end user gets very little value out of it. If anything, there is a real possibility that the user will be exposed to malicious pages and content through some of the ads served by the dubious ad networks that use similar tricks to propagate their content.
In a lot of cases, users will be able to disable the notifications they agreed to from inside their browser. In other cases, the user may need to run a dedicated anti-malware application and let it handle the situation and take care of the intrusive pop-up ads for them.
At any rate, any page or ad network that relies on tricking visitors into allowing ads and notifications should obviously be avoided.