How do you know when a banner comes up saying you have to notify someone for being hacked is fake?

A couple times in the last month a huge banner has popped up in the center of my screen saying I’ve been hacked and all my “banking information, credit card numbers, passwords and my life is at risk” unless I call a number they provide. The way I get rid of it is too complex to report but how I know it’s fake is I read every sentence and I can pick out the grammatical errors. And they are few and far between. Infuriating.