I am confused as to the need for security software (anti-virus, anti-trojan, anti-spyware, firewalls, etc) for my new iMac. Many books and online articles state that such software is essential, however other articles and, perplexingly, store salesmen say that such utilities are an unnecessary waste of memory, as the threat is simply not there. Who should be believed, and what would you recommend? I am running Mac OS X Leopard (10.5.6).

This is a very good question and one which often sparks debate within the Mac community. Before dealing with answering your question pertaining to Mac, let’s take a look at the need to run such security software on a Windows-based computer (as this will provide the context for our discussion on the same issues relating to the Mac operating system). The opinion of the vast majority of computer experts is that if you are running Windows then you absolutely must run a firewall and antivirus software. For the firewall, at the minimum you should run the in-built Windows Firewall. However, in most cases I would recommend that you complement this with a broadband router that supports Network Address Translation (NAT), a feature of almost any router you purchase, as this itself provides a layer of protection. There are also plenty of other third-party software solutions available. That said, I often find that such third-party solutions are memory and resource hogs. If you are running the Windows firewall together with a NAT router then this is often the best of both worlds – offering good protection without unnecessarily bogging down the computer. That said, the third-party software based firewalls often provide additional functionality such as stopping the user from doing potentially dangerous things or visiting dangerous places. Therefore, you need to weigh-up these additional features against your needs, while also considering the performance hit which may occur on your computer. Regarding antivirus on a Windows-based computer, this is also essential given that the vast majority of viruses are targeted at the Windows operating system. Finally, it is also essential that you keep a Windows-based computer up-to-date with the latest Windows Updates. These are often security updates which will patch against identified security threats, making the operating system more secure and resilient against attack.

The reason that it is important to be running security software on a Windows-based computer is most attacks are targeted at this platform. Why this is so has many answers. The most common being that Windows has the greatest share of the operating system market and therefore has the greatest number potential victims. The creators of malware, viruses and other security exploits wish to target the greatest number of potential victims and therefore select to target their attacks against the most common operating system. Previously this was a good reason to not run antivirus on Macs, since Mac OS had a relatively smaller share of the entire market. However, with the growing popularity of the Mac operating system, helped in part by the explosive growth of devices such as the iPhone which are leading more and more people to consider switching to a Mac, it is now becoming a more attractive target for attackers to consider. While Mac OS X is considered a relatively secure operating system there is no reason that attacks could not start writing and distributing exploits for this operating system, much like they have been doing for Windows over the past few years. In response to the increase in usage of the Mac OS X operating system, security experts have started to recommend that Mac users should consider running antivirus on their computers. There is quite a bit of sense in following this advice, since antivirus is often a box that needs to be ticked so that you have peace of mind in that you are protected against any existing (no matter how limited they are) and emerging threats. Additionally, it is possible for Macs to spread viruses to Windows-based computers. For example, if you receive an email with a Windows virus then, since you are running a Mac, you may not become infected. Additionally, if you are not running antivirus software on your Mac then you may not be alerted to the presence of a virus in the email, as many of the Mac antivirus utilities can also detect Windows viruses. If you then proceed to forward that email to other people then you may be (unknowingly) spreading that virus. As such, running antivirus on your computer is part of being a good citizen to help curb the spread of viruses.

There are many different antivirus packages available for the Mac and a search of Google will assist in finding the various different utilities. Since there are substantially fewer Mac-based antivirus utilities than Windows counterparts there should be quite a few reviews on each of the utilities. Therefore, before installing or purchasing antivirus for the Mac I would recommend that you read a gamut of reviews on the different antivirus utility offerings for the Mac platform. In particular, you should pay attention to the protection offered by each utility together with the performance and resource burden which they may place on your computer.

However, as we discussed when looking at protection which is required when running a Windows based computer, antivirus is just the tip of the iceberg. In addition, I also recommend that you enable the Mac OS X firewall on your computer. Many people do not realise that Mac OS X comes with an inbuilt firewall. While the chance of something happening to your computer through a network exploit is minimal, there is no reason not to enable all the security on offer. Additionally, this should not adversely affect anything, assuming that you are not attempting to use your Mac as a server or access your Mac from another computer or device (this is unlikely in most cases, but if you are then you can set firewall exceptions). To enable the Mac OS X firewall, go to the Apple menu > “System Preferences”. Open the “Security” preferences panel and click the “Firewall” tab. You should see a “Start” button allowing you to turn on the firewall. If this is greyed out, click the padlock icon in the bottom left-hand corner of the window and authenticate. Once the firewall status has changed to “On” with a green light then the firewall is enabled. Should you need to set any firewall exceptions in the future, click the “Advanced” button. Now that the firewall is enabled you may occasionally find a message appears asking whether you would like to grant a certain application permission to allow inbound connections to your computer. This was being allowed by default previously, because you were not running the firewall. However, now that you are running a firewall it is intercepting this traffic and seeking your permission. If you understand what the application is trying to do and wish to grant access then click the “Allow” button. Otherwise, click the “Deny” button. If you are unsure I would recommend clicking the “Deny” button and see what happens. If you find that access is actually required, then restart the application and it should prompt you again, at which time you can allow the connection.

Finally, as with Windows, it is essential that you keep your operating system up-to-date. Regularly run Software Update to check whether any updates are available for your computer, as it is particularly important to ensure that security updates are installed. If you are still running Mac OS X Leopard then you may also wish to consider upgrading to the latest version of the operating system, Mac OS X Snow Leopard (10.6) which is currently at point version 10.6.2. This new version of Mac OS X does not have many major feature improvements, but was primarily designed as a release which improves the back-end performance and stability of the operating system. That said, there are some very nice little improvements to the user interface and functionality which do make this upgrade worthwhile, not to mention the improvements to the operating system kernel itself which should provide you with some performance benefits. Furthermore, given the relatively low price of Snow Leopard ($39.00) this makes it quite affordable to keep with the latest and upgrade to Snow Leopard. However, before upgrading I would suggest that you check that your applications will function correctly on Snow Leopard. When first released there were some compatibility problems. That said, Snow Leopard has now been available for long enough that most software developers have released updated versions to resolve any problems. However, it would be prudent to double-check.