Finally decided to install an AV app, namely Sophos, which offers a free home edition for the Mac. This version is 8.0.2.
It immediately downloaded over 11 MB worth of 'updates' (which I presume are the honking big list of virus/worm/Trojan descriptions available to date). Sophos claims to be protecting against 3,479,000+ threats at the moment.
Now it's scanning ca 2 million items on all my local drives (including backup); this is likely to take 8 hours. So far no 'threats'.*

* And it just now finished scanning everything — ca 5.5 hours — and found nothing nasty to report.

I probably should have dropped this into THE CYBER-SECURITY THREAD in the Lounge where most of the discussion is taking place; but this is specific to a brand, so I dropped it here. If a moderator thinks it needs a different 'home', I've got no objection.

Last edited by grelber; 04/26/12 09:11 PM. Reason: Update