Im getting a lot of this kind of stuff on my mobile but only when on AB, sometimes when browsing FB it will close FB and open AB to display this message. The Ed really needs to get this sorted!! it appears that it is being ignored, maybe I'm wrong!?
Chrissa if you look about here there have been loads of threads since the weekend about people getting all this stuff non-stop on AB. I posted one, so did pasta and several other people. Have a look in Ed's blog for starters.
It is where people "lock" you out of your computer, phone or tablet and say they wont release it until you pay them some money.
I have had it a couple of times on my PC, and my son had it a few months ago where it totally locked him out of his PC.
This is why you should ALWAYS back up important files on any devices just in case you need to do a "factory reset" to clear out the device and start again.
I dont think this is ransomware, so far no one has asked for anything apart from wanting me to buy an iphone, which I wouldn't touch anyway. If I push the back button it goes away for a while but then returns!