I've also received the exact same message today, which led me to this forum and your post. It appears to be a genuine email as it has my correct a/c no., from firstname.lastname@example.org. Am still running a complete system scan but it has so far come up with nothing of any real concern - tracking cookies only.
I suppose my Virgin a/c could be hacked and a scam email sent. I'm not sure what the point would be though, other than to send an alert. I notice it did direct me to their subscription-based security package....
I do feel prompted to review all my important web passwords, replacing them with much more secure ones. These days it just doesn't seem worth taking risks and it's easy to get complacent.
Sorry this probably isn't much help, but just wanted to let you know.
Not really sure what this is all about in all honesty and as you say it all looks to be a genuine email though no one has responded to this thread as yet to confirm. Pretty sure I have scanned everything connected now and still nothing showing up.
I've had several paper letters recently warning me of a "malware infection" related to "generic/avalanche". Also the letter refers to generic/avalanche as "a piece of malware", in fact it isn't any one specific bit of malware, rather a somewhat overly generic classification of a set of behaviours of software. The thing is, there's lots of legitimate software that exhibits the same behaviours as classified here, so there's a very good chance if you are using other anti-virus/anti-malware software that this is a false alarm.
A straw poll of some 20+ other virgin media customers (friends, colleagues, neighbours) suggests they (almost) all started getting similar letters from Virgin around the same time. Coincidence?
As such, I have complained to Virgin about this being scaremongering tactics to sell additional services, and I have submitted a complaint to that effect to the ASA.