This site has a good feel to it. Am wondering if any here are using the software. A license to use it is free. Must be renewed (also free) after one year.

https://www.avast.com/en-us/free-mac-security

To install it, any other anti-virus software (e.g. ClamXav) must first be completely uninstalled.

I've never found it either necessary or otherwise desirable to install anti-virus software, so I can't comment on this or any other app, but the first two posts here, even without regard for some of those farther down the page, would be deal-breakers for me if I were looking.

That requirement would certainly give me pause. Suspicious and unnerving.

So, here's my experience. Except for ClamXav I have never left any virus checker installed. I've found they affect the performance of my machine by slowing it down. Sophos was the most serious offender.

I have used Avast, and it was quite simple, although I did not uninstall ClamXav and it was broken afterward. I definitely would not have used Avast if I had been aware of the data mining aspect.

Except for ClamXav, I have got into the habit of only using a virus checker periodically, perhaps once a year. When I do, I install the software, do a complete scan, and then uninstall. However, It has always been a fruitless exercise as the machine is always clean.

So, I'm coming around to Artie's way of thinking and may simply stop altogether. Well, may not altogether....I'll likely always keep ClamXav. And that may only be because I'm a notorious cheapskate and, having contributed to ClamXav more than once, I'm just getting my money's worth.

I thought ClamAV was running in the background on a base OS X installation?

If that query is directed at me, I wouldn't have a clue. I was merely responding to OP's comment.

it was on the mac awhile ago, but it had been somewhat depreciated and it looks like it's been completely removed (as I look for it in 10.9)

I guess Apple figured gatekeeper was adequate?

Now I have zero clue as to what's going on. It certainly doesn't have anything to do with me.

I've never been aware of anti-virus having been included with any version of OS X. (EasyFind doesn't find any reference to ClamXav in 10.6.8.)

I distinctly remember seeing "freshclam" somewhere in osx in the past.

A Google search turns up lots of "freshclam" hits, and a cursory look suggests that it relates to ClamAV. (Example: man page freshclam section 1)

yep I thought freshclam was the definitions auto updater or something. it's possible that got installed by something else on my systems at one time or another, but I was thinking it was stock for a time. One of those "not fully implemented features" of earlier OS X, where had there been an actual virus show up, a minor security update could have activated it. but that never turned out to be necessary.