Thanks Mike Bracknell.
The curiosity is – or rather was - that the spammed address book is not on my computer but somewhere in the bowels of Yahoo. It is only that contact list that has been accessed and abused. The computer I normally use is kept well updated and protected and demonstrates no signs of infection or problems.
On the morning of seeking the wise counsel of the Pprune expertise I was in a rush and failed to find any explanation in a brief Google, however, I have since found that this is not such an unusual problem and is apparently caused by hackers somehow gaining the password to the relevant Yahoo, Hotmail or similar accounts.
Quite how that is done I did not establish though it would seem to be a relatively easy task and does not necessarily infer that any user computer has also been invaded. Famous last words…
Having established that much, I take the opportunity to convey my somewhat Arabic influenced affections to the spamming community; May your balls turn square and fester slowly from the edges inwards.
jg