Fake windows tech support at 844-354-5841
Popups tell people to call them to fix non existing problems:
I'm getting an Internet Explorer window locked open saying it's missing a file, and to call a tollfree helpline at 1-844-354-5841
https://answers.microsoft.com/en-us/protect/forum/all/cant-update-windows-defender/45138714-3d0b-4843-9f24-71924d62e2fb
Other complaints:
http://findwhocallsyou.com/8443545841
https://www.okcaller.com/8443545841
https://social.technet.microsoft.com/Forums/en-US/c45d96b7-10b6-4b05-9f68-c0fad6a8bba7/malware-missed-by-yesterdayampamp39s-windows-defender-and-todayampamp39s-ms-safety-scanner?forum=mata
Time for revenge:
https://bobrtc.live/phonebook/dial/18443545841