Do I need to instill anti virus program with iMac

Have a look at this thread: https://discussions.apple.com/thread/4198016?answerId=19233381022#19233381022

Opinions differ but follow the links to klaus1's and Thomas A Reed's tips/articles and you'll get good advice.

FWIW, I occasionally run clamXav - more out of interest than necessity. Never found a problem.

I believe you will find the general concensus is no. Just keep your system up-to-date by running Software Update often and it will be fine. I have ClamXav installed on my system too but never run it because there was never anything for it to catch.

Turn on the Firewall and enable Stealth Mode. I'm not running ML, but for me it's located in System Preferences>Security. Also, turn off all Sharing, if not needed.

The safest is to be behind a router. That way, only the router is exposed to the Internet.

Since Apple Mac's are constantly gaining market share and taking it away from PCs, many people have decided to start making viruses for the Mac. The reason the Mac has been known to be so secure for all these years is because it was insignificant compared to the market share PCs have had. Not because the Mac had impenetrable hardware. And there is adware, malware and bloatware that can affect Macs as well as Windows computers. Even some exe files even when not opened may affect the Mac.

So with the increasing market share of Macs, viruses are becoming more common for Macs (the most signifigant and infamous of them being the Mac Defender virus), so look into some anti-virus software. You don't need to spend a ton of money on expensive anti-virus software, like ESET, which detects files as viruses that are SIMILAR instead of exactly the same as a known virus. This can cause overdetection causing you to delete files you don't need to delete. And since Mac viruses aren't rapidly changing, yet, it's useless.

Although Avast! isn't very good for windows (it detects software that isn't even a virus, this is a problem on Windows XP especially, it detects some essencial system files as viruses...?? Not on a mac though) it's great for mac. Try it out.

The firewall is off by default and should be left off if you're behind a router, on a network where you may want to provide services. Its only real use is on portable Macs that are sometimes connected to untrusted networks, such as a public hotspot.

I know it's superfluous, but I'm behind a router and the firewall is on. I've been like that for maybe three + years. As far as I can see, doesn't change a thing or make the slightest difference. Why should it be left off?

Because it can cause time-wasting alerts, wastes cycles, and serves no purpose whatsoever.

Linc Davis wrote:

Because it can cause time-wasting alerts, wastes cycles, and serves no purpose whatsoever.

Maybe turning it off is more elegant, since it's superfluous, but have never had any of that.

Never heard that either, but I don't doubt it.

Thomas Reed has an in depth article on this subject, as well. http://www.reedcorner.net/do-i-need-a-firewall/

Message was edited by: MadMacs0