I had the following email - minus the black blobs - waiting for me when I checked in earlier this morning.
It was from a friend, had no malicious attachments, and so hadn't been consigned to trash or the spam folder.
The content wasn't what I'd expect from that friend so that helped to confirm that it wasn't an email they'd consciously sent me. I made contact and, sure enough, they were fully unaware of the fact that the message had been sent from their personal email account to multiple recipients from their address book.
The implications of this are that the email account had been hacked and/or their computer (an Apple Mac) was infected with some virus or trojan. My advice was to assume the worst; both to be correct and act accordingly. I also advised them to contact everyone who will have received a copy of the email advising them of the situation and to delete the email without reading since the link it contains will, no doubt, be a fast-track to further woes.
For the email account the quick fix is an immediate change of password, preferably using a strong one which at least meets their service provider's recommendations.
Their response, when I suggested the possibility of a virus infection on the Mac, was surprising. They'd been led to believe that "Mac's don't get virus infections" which, apparently, came from the sales assistant. I set them straight on that piece of misinformation and advised they assume the worst and get it checked out even if it is unlikely to be the case. I think they're planning a return visit to the shop within the next few days and will, I suspect, provide some relevant customer feedback.
Intego, Kaspersky and Symantec all offer highly rated security solutions designed to keep your Mac as clean and pure inside as it looks outside. Intego's VirusBarrier 6 offers protection for 2 Macs about £70, Kaspersky's One product will run you about £25 and the Symantec product is about £30 for 2 Macs. All three offer comprehensive anti-malware protection.
If these are too pricey, Sophos and ClamXav are available for free. If you're new to anti-virus software (and most Mac users are) you might want to try a free option to learn more about what's available to you.