Sorry this isn't a thread on general photography discussion, but I couldn't find a better home for it.
There is a good chance that quite a few have already heard of this, but if not --
It first appeared around January this year but has recently resurfaced in the UK and Germany and possibly/probably elsewhere too.
It takes the form of an on screen message that says (in the UK) Metropolitan Police and Strathclyde Police investigations have detected activity from your PC involving illegal sites, possibly pornography, child pornography or terrorism involving Alkaieda and your PC has been locked. To unlock the PC you need to pay £x and it tells you how to do it. Sometimes the message includes what look like police logos.
I'm sure none of us would be taken in by it, but you may know someone who uses a PC but is less Internet and PC savvy and may be worried by it, especially as it appears to have links to the police. So if you hear of anyone who has this little nasty do tell them that it is a scam and under no circumstances should they pay anything.
My PC got it about a week or so ago - I'm guessing from a link on a webpage somewhere that may have included a misdirection - and it does stop all access. The machine will apparently boot up OK, but then goes into the message page and you cannot do anything - the Taskbar had gone AWOL, keyboard does not work, there is no mouse cursor, you can't get to the Control Panel. The only thing you can do is use the big button to turn it off.
Fortunately it is easy to remove. Malwarebytes, which is a free security program, finds and destroys it
If you don't have it already I'd recommend it. Free, small and runs quickly.
Bootup in Safe mode and run Malwarebytes and the problem is solved.
Must admit I had a bit of a chuckle at the message. The idea that the police would find activity of the types described, tell you they had found it and then give you your PC back so you can continue, if you pay up.
And "Alkaieda" LOL - I think I used to take that for hangovers!
Have a good New Year all and lets be careful out there.