That's a tech support scam popup!
Can you close the browser using Task Manager?
Any browser extensions that need to be disabled?
Fake Tech Support Scams – see video from the MS Digital Crimes Unit (copy/paste the link into your browser). https://www.youtube.com/watch?v=hQpm2ldzUno
https://blog.malwarebytes.org/fraud-scam/2014/11/psa-tech-support-scams-pop-ups-on-the-rise/
For issues with "tech support scam" popups if using Edge see the Answer of GreginMich dated
June 20, 2016: http://answers.microsoft.com/en-us/protect/forum/protect_other-protect_scanning/1-888-2361-scam/0990122e-61a9-431b-947e-a904c202fa7c
For issues with Google Chrome see How to stop unwanted pop-ups or homepage changes in Chrome,
and How to reset Google Chrome settings. You may want to use https://www.google.com/chrome/cleanup-tool/
If you cannot resolve this issue see this free multi-step removal guide from Malwaretips.com: http://malwaretips.com/blogs/remove-tech-support-scam-popups/ and
follow the instructions on how to close the popup. Remove Tech Support Scam pop-up
ads from Windows PC If the issue continues then follow the step by step instructions in the guide on removing malware. You may not need to scan with Hitman Pro (available in trial version if you do need to use
it). If scanning with AdwCleaner (step 1), Malwarebytes Free (step 2) does not eliminate the malware problem, then you may need to reset your browsers:
https://malwaretips.com/blogs/reset-internet-explorer-settings/
https://malwaretips.com/blogs/reset-chrome-settings/
https://malwaretips.com/blogs/reset-firefox-settings/
http://www.howtogeek.com/237527/how-to-reset-microsoft-edge-in-windows-10/
Regards...
http://blog.emsisoft.com/2015/01/27/top-10-ways-pups-sneak-onto-your-computer-and-how-to-avoid-them/
