How did this happen?

I haven’t used my iMac for over a week - it was in sleep mode. It refused to wake up yesterday, but after unplugging, re-plugging and rebooting I found that I had Avast installed. I haven’t downloaded or installed it. How did it get there?

Did someone else have access to that Mac or is the Mac used by multiple persons?

Avast will never force install a Software of them on your machine for sure.

Also did some other software get installed recently?

avast doesn’t install itself just out of the blue.
Someone must have triggered the install.
If you had avast installed in the past, you likely haven’t removed it (completely)

Thanks for the swift replies.

The iMac is a private computer which I use primarily for score-writing: it was last used on 14th Sept. No-one else had access to it. I use my MBA for Email and general use. I checked my Downloads folder, and there’s no sign of Avast being downloaded. There’s no sign of activity at all during the week until the work I did yesterday (24th). In the Apps folder, Avast claims to have been created on 23rd Sept. No-one was at the computer at that time.

I have never felt the need for anti-virus software on the Mac, so I am as certain as I can be that I have not (knowingly) installed Avast in the past. Indeed I didn’t even know what Avast was when I found it, and had to look it up.

What other installations might let Avast in?

Thanks!

As far as I know avast doesn’t come bundled in any other application install.

Recently, Avast for Mac IS distributed with some other SW, but it should be always optional.
The question is thus - “What SW did the user install in the last time?”