Yesterday I received an email from a friend which included an unusual looking link on a subject that I didn't recognise. I didn't click on this link but instead contacted friend to ask if he really had sent it. He replied that he hadn't and that a number of his contacts had had similar emails purporting to come from him. His reply was, "Don't open it! I think I've been got at!"
I immediately deleted the email in question.
OK, so as far as I know, no harm done to my computer or email but my friend's question was what should he do if, as it appears, his email has been hijacked?
He has run Malwarebytes and all is clear.
Change his password immediately, that's what he should do; and to something that is not a name. Include one number and one capital letter. If the same password has been used elsewhere he needs to change that too.
Not an expert in these matters but I suspect if your email address is known, it can be spoofed. If the account has been broken into a password change locks the intruder out. But it seems to me that if someone grabbed your friend's contact list, the damage may have been already done. Wait and see, may need to create an alias to use if you continue to receive dodgy emails from them.
I don't think your friend's computer or email account has necessarily been hacked. There are scores of places around the net where an eavesdropper could have picked up a copy of one of your friend's emails to multiple addressees while it was in transit, and from there, the fabrication of a message such as you describe would be easy.
Can't understand why lots of Ab'ers seem to think Malwarebytes (free) is the bee's knees of virus protection.
My experience with this "freeware" is "it's a load of cr@p".