Flashplayer linked virus, malware
I have something like a virus in my MacBook air, (Siera 10/12) that keeps insisting I download a new Flashplayer. I downloaded a new Flashplayer via Adobe, but I'm still getting the messages.
I've installed a new McAfee package, Malwarebytes, Apple security, but no fix.
The bad software inserts new ads onto webpages, prevents me from closing tabs or going back to prior pages, and gradually slows down the pages. I've found it on Chrome and Safari. It also keep asking if I want to close down particular pages, and sends me little threatening notes.

