It's not as easy as clicking "No".The rule of thumb is to never trust anything on the internet ever, especially when it involves clicking "Yes."
Click "Yes": Your infected.
Click "No": Your infected.
Click "Yes": Your infected.
Click "Cancel": You're infected.
Click "Yes": You're infected.
Click the red X at the top right: You're infected.
This is how I suspect a lot of malware gets transmitted. People need to realize those buttons can say whatever they want, it makes no difference. They're just programmable buttons, there is nothing magic about hitting "No". I can program "No" to do whatever I want it to do, and that includes making it do exactly the same thing as "Yes" does.