This week, we explain why fraudsters impersonate celebrities, attractive young people, and sometimes even your friends in a bid to connect with you on social media.
How does it work?
Sir Cliff Richard has this week become the latest in a long line of celebrities forced to warn fans not to accept friend requests or reply to messages from people pretending to be them on social media sites such as Facebook and Twitter.
The 76-year-old singer issued the warning after learning that fraudsters were impersonating him online in a bid to persuade his fans to transfer money for bogus fan club memberships and updates.
"It has come to our attention that there are people purporting to be Sir Cliff on Twitter and Facebook, who have befriended fans and in some cases tried to trick them into handing over money," the star's official Facebook page said.
"We suggest that you do not accept any friendship request from any account that uses the name of 'Cliff Richard'."
Not all social media friend request fraudsters pose as famous people, though. Some pretend to be beautiful women, or even send out fake requests from people already on your friends or contacts list.
However, the aim is generally the same: to convince you to hand over money, trick you by sending you a malicious link, or persuade you to share information they can use to defraud you at a later date.
Child abusers are also known to use this tactic to befriend young social media users by pretending to be children themselves.
How can I avoid being caught out?
Celebrities are very unlikely to contact you on social media asking to be your friend, even if you're a massive fan. So be very wary of any requests coming from famous people.
You should also look out for friend requests from "models", or attractive young people, you - or your children - have never met.
If, meanwhile, you receive a friend request from someone you are already connected to, it's worth trying to contact that friend separately - on another app or by email, for example - to double check that the request really has been sent by them.
I've been defrauded. What should I do?
If you accept a request to connect from someone who later turns out to be suspicious, the easiest way to deal with it is to delete that person from your contacts list - and report any dodgy messages or requests for money to the site in question.
If, on the other hand, you think your computer has been the subject of a malicious attack of any kind, it's definitely worth running an online virus scanner, such as the Microsoft Safety Scanner.
It is also important to change your passwords and login details to prevent hackers accessing your accounts.