What a humdinger of a virus – encrypts all Office documents on the machine and switches the login screen to a ‘West Yorkshire Police’ logo and a ‘Pay Now’ button. The very cheek of it! Mcaffee does not know anything about it. Fortunately, Kaspersky have an app to fix it – http://support.kaspersky.com/faq/?qid=208286527 – and it does appear to work. Preventing the nasty login screen from reappearing is simply a case of renaming the executable, which gets dropped within your AppData folder under a randomly generated path.