My computer screen froze, multiple windows appeared advising my computer was open to attack from malevolent adware and Windows defender blocked it . The phone number said was Microsoft support and to contact them urgently, said not to shut down or restart my computer as spread the virus, also had a login screen for me. I checked Microsoft support numbers and not a Microsoft support number. Contacted Microsoft support via my phone and a scan said no issues detected so I shut computer down, rebooted and conducted a manual scan, no issues found. Tried to trace number but no luck so far.