It's amazing that people still fall for this crap in this day and age, but anyway, it seems that scammers are emailing people pretending to be part of Mi5 and asking for money. Clearly, it's a problem, because pretty much the most prominent thing on the Mi5 website at the moment is a big notice telling people to not send money in reply to these emails. Duh.
The notice is the most prominent thing on the Mi5 website at the moment, above such trifling matters as the national threat level or the always-interesting Mi5 jobs page. Specifically, the notice says:
Members of the public in the UK and abroad have received requests for money by email or phone from individuals claiming they work for the Security Service (MI5). Some have purported to be from MI5's Director General, Sir Jonathan Evans. These requests are a financial scam and have nothing to do with the Service or the Director General. If you receive such a communication, please do not respond to it and report it to the police.
Mi5 haven't actually said what sort of fishing attempts are being used here, but given that it's Mi5, ransomware would be a pretty safe bet. As noted on this spamming blog:
It might have been useful to know more about the type of scam the warning refers to. It could, after all, be anything from a 419 to some form of ransomware, and the ways of recognizing and dealing with those different kinds of scam can be very different. But I have yet to find an actual example.
To be clear, though: if you get a 'request for money' from some dude pretending to be the Director General of Mi5 (and you're not a secret undercover Russian spy), IT'S A SCAM. Got that? Cool. Now, where was I with that nice Nigerian prince.... [Mi5 via The Register]