Of all the good advice I received—and it was all very welcome—@hawaii_jake had the best response (to suit my case). Malwarebytes did find the trojan horse virus that I was infected with (AVG anti-virus had not found it) and cleared it. The download was free, I ran the scan from the defaults, and three hours later (while I slept) the infected files were flagged and noted, for my selection and removal this morning.
Sending that bulk email notification to my list of contacts was fairly problematic. I had 550 addresses in my address book, most of which I never actually use any more. I had more “undeliverable mail” errors than I could shake a stick at—which also made the process of mailing them out to be a chore. (I’m surprised that my address book didn’t kill the spam mailer.)
And since I always use the bcc: address for the few bulk mails I do send out, that advice (as good as it is) was superfluous to me. But that is excellent advice. I cringe whenever I get a bulk mail from a friend with my name in plain sight.
But this has given me some very good ideas to apply to my own system:
1. Put bunches of “known bogus” email addresses at the top of the address book and at various other points, too. Anyone who attempts to send mail to the entire list will hit a wall of errors to start with, and that will at least slow them down. (I’m sure the spambots overcome this with relative ease, but those errors have to at least slow them down.)
2. Sprinkle some fake “contacts” containing your own email address in your address book. (As it happened, when I got to work this morning I did find where I had spammed my office address from home, because I often send mail as a simple reminder from home to work and vice versa.) If I had my normal “at home” contact information stored under “Joe Blow”, then I would have known about this as soon as it happened—as soon as the spam was sent to “Joe Blow”—since I was apparently online as it was happening.
Thanks again to all who responded. Yeah, it wasn’t as serious as a fire or flood, but it made me feel for a short while the way I did when my car was burgled in my driveway—a shock to the system.