Is ScanGuard a legitimate antivirus?

Depends on your definition of "legitimate."

My definition of "legitimate" doesn't include things that are completely useless on a Mac, and whose only functionality could make your Mac unstable. So, I would say, "no, it's not legitimate."

Pass on what? The link is to an article written by one of our senior helpers here advising how to protect your computer. Why pass on good advice? The article directly answers the question you pose in your original post. Why ask the question if you are not wanting the answer?

Fully agree with Bob. John Galt's document is crammed with excellent information. I strongly suggest reading it. And I don't just mean you. Any computer user should read it, no matter how experienced they are.

Effective defenses against malware and other threats

Hi,

Third party so called anti virus software should never be installed on a Mac. Your Mac has built in security.

Pass on what?

I assumed she meant pass on ScanGuard.

I didn't assume anything. I took her at what she said in response to my suggestion.