If you are running on the latest Mac OS X at home and you allow Apple to automatically update Mac OS X on demand, then my advice is No, you don’t need anti-virus protection on your Mac at home, well not at the moment anyway. Apple themselves go out of their way to state Mac OS X is not effected by viruses and protects itself from other malicious applications -
"The Mac is designed with built-in technologies that provide protection against malicious software and security threats right out of the box" - Apple.
A word of caution with my view, which will be highly controversial to some, the Mac malware situation could change in the future should the bad guys decide to target the Mac OS in anger. Theoretically this may happen if the bad guys started to find they aren’t getting any joy out of attacking Microsoft Windows PCs, however this is currently not the case, there are no significant shifts in the malware OS attack vector occurring. In my view, I feel the bad guys will actually move onto targeting the smart phone market in the future, of course this is a market which is well occupied by Apple. In the meantime Mac users should guard against complacency, especially when considering all software will have it faults and therefore will have vulnerabilities to be exploited. Where we have an operating system, we are talking hundreds of thousands lines of code, which is ultimately written by human beings, so it can never be perfect, while operating systems by their nature are a highly complicated pieces of software. So it is safe to conclude no operating system can never be regarded as being ‘secure’ and therefore cannot never be guaranteed to be vulnerability free; there is just no such thing as 100% security. The answer to this problem is to continually fix (patch) the operating systems as vulnerabilities become known, hence the importance of ensuring your Mac OS is automatically updated. Going back to the lead question, today if I was a ‘home’ or mobile Mac user running OS X, I personally wouldn’t bother with deploying anti-virus protection,
as the risk is currently extremely low, while Mac OS X itself does have good malware protection built in. I certainly wouldn't criticise anyone who wants to deploy anti virus on your home Mac as matter of precaution, of course the trade off in doing this is an impact on system performance and the cost of purchasing an anti-virus product.
Why aren’t Macs at the same risk of Windows
The fact is the vast majority of malware (including viruses) are written specifically to exploit the world’s most popular operating systems, namely the Microsoft Windows range. There are well over a million documented* “viruses” which specifically target the Windows operating system, while there is only a handful of known viruses which targets the Apple Mac operating system range, and of these, some are actually concept malware produced by good guys, but to my knowledge none currently work against the latest version of Mac OS X. The folk behind writing and deploying malware target the largest market share and the lowest hanging fruit, namely the easiest OS they know is the easiest to exploit from. Microsoft Windows operating systems are by far the most used operating system on this planet and has arguably been one of the weakest for security in comparison to other operating systems like Mac OS.
A third point often raised in this debate, is Windows users are less technologically savvy than Mac users (in other words more stupid!) and therefore are more easier to be "conned" into clicking links which execute and install malware. I think this might have been true in the past, but today I note that many non-techies are using Macs, many people are simply choosing a Mac over a PC as a status or even fashion symbol, so I no longer buy the PC users on average are more stupid than Mac users argument.
Anti Virus Protection is no Guarantee
Anti virus does not guarantee complete protection against all known viruses and malware, AV protection is only as good as AV's latest update, and even then may not be able stop all of the latest malware. So you could well have anti virus installed on your Mac which is bang up-to-date, but if a new type of virus suddenly appears on the scene, the anti virus may not detect the virus anyway, the truth of how ineffective some anti-virus products on Windows PCs is actually quite alarming, but I'll save that one for another post.
Do business Macs need Anti-Virus Protection?
The short answer in my opinion is Yes. Medium to large businesses which have Apple Macs deployed in a mixed Microsoft Windows environment, may well want to consider deploying and running anti-virus protection on their Mac estate.
Why? Macs have been known to harbour Windows based malware, malware which could make its way from the Mac via file sharing on to Windows PCs. Just because Windows malware does not work on the Mac, it does not mean it cannot be stored on a Mac drive, and if that Mac has no anti-virus protection, then the malware files on the Mac drive are never checked for Windows malware, which in turn means the malware files are never removed, and leaving any Windows malware present and dormant on the Mac drive. Should that malware data file make its way onto out of the Mac drive, perhaps via a network share, USB memory device, or server storage, and then onto Microsoft PCs, then there can be real issues in store for the PC estate.
Also there are information security regulations and standards which insist on the deployment of anti-virus protection regardless of the operating system and your perceived risk.
Where can I get Mac Anti-Virus Protection
If you feel you need anti-virus protection on your Mac at home, or within your business environment, most of the usual big commercial anti-virus vendors provide a Mac OS anti-virus client, personally I'm independent of security vendors, which is important, as I try to keep my advice independent and objective, so I'm not going to be suggesting any vendors here. But there is a free home Mac anti-virus client called ClamXav - http://www.clamxav.com/, as I said in my blog post last week, I believe anti-virus protection should be free for all home users and provided out of the box by the OS vendor - http://blog.itsecurityexpert.co.uk/2010/04/home-anti-virus-is-completely-free-as.html
The Biggest Threat to Mac Users
Finally home Mac users should be still be wary of attacks made through their web browser and their email client. For instance phishing attack is just as likely to be successful against a Mac user as it is a Windows user, always remember many online fraudsters are targeting your personal information, your credit card details and your online bank account login details, which are often obtained through attacks through web sites (the web browser) or through the Email client, either way by conning the person into sending the details. Some third party applications on Mac can also provide a way in for malware, such as file sharing apps, to be wary about what you agree to install.
This is an interesting topic, and has been hotly contested in the security industry for years, especially between AV vendors with Mac anti virus products to pendle, and Apple enthusiasts (BTW I'm neither!), so if anyone has any different views whether in agreement or not, or indeed recommendations, please post in the comments - Thanks.
* April 2008, the BBC News reported Symantec now claimed "their anti-virus programs detect to 1,122,311 http://news.bbc.co.uk/2/hi/technology/7340315.stm