How do you scan for virus on an iMac?

You shouldn't have to but you can try these:

1. Malwarebytes
2. DetectX Swift
3. Remove adware that displays pop-up ads and graphics on your Mac
4. Stop pop-up ads and adware in Safari - Apple Support

Mac OS was designed from its very beginnings to be extremely secure. If simply kept up to date and otherwise left alone it will remain so. Using common sense also helps to keep Mac OS trouble free. By that I mean do not download anything from sites you are not familiar with. In addition do not use a torrent, respond to any e-mail, pop up, phone call or text that says your computer is at risk. These are ALL scams!!!

Simply enjoy your Mac and if you are like the majority of users your computer will remain trouble free for years!

Exactly what is the difference between a virus and malware? A virus is a form of malware, but malware need not be a virus.

There are not Mac viruses.

However, you can scan for malware.

Download and run Malwarebytes | Malwarebytes for Mac

It's free and only takes a minute or two.

Your welcome.