Assuming you run no other programs at that moment and have no other sites open in Chrome, it's either your PC that is infected, or the site you're visiting, or the mails you have open. Your PC is the most likely candidate.
- Try another browser
- Reset Chrome if other browswers are OK: https://www.google.com/search?q=reset+Chrome
- Try the full recipe from Grif: https://www.cnet.com/forums/discussions/unknown-webpages-pop-up-on-my-computer-screen/#post-e0f48479-292f-49c8-8bb3-5e7ab6818839
I've been receiving these internet security alerts since last week; they're annoying; the screen turns red and this message is repeated several times telling me my computer has become infected; do not attempt to shut your computer down; blah, blah, blah.
I did a forced shut down then a restart and immediately scanned first with SuperAntiSpyware version 6.0.1254 and then with Avast free antivirus and both scans detected nothing; no security threats. It mainly happens while I'm checking my AT&T webmail. I'm currently using Google Chrome as a browser.
Anything else I should be doing to check to see if my Dell laptop is infected? My laptop is a Dell Inspiron 15-3000 Series and currently I'm using WIN 7 Pro which came installed on it; there is also WIN 10 but I like using WIN 7 Pro because it acts like the OS on my previous laptop which had WIN Vista.