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.