These days, suddenly many web pages "can't be opened" when I surf the Internet. At first, I didn't pay attention and didn't look carefully. Later, I found too many websites are "unavailable", which made me feel strange. After carefully examining the so-called error 404 page, I discovered the "Network Guardian". In the middle of the page, there is first a "friendly reminder" saying that the webpage contains unsafe factors, etc., and below it is a bunch of ads...