1. Your mac has built in security that is very effective. You do not need to add anything. Just keep up with the software updates from Apple and you will be fine. If you use a router, it already has a firewall, and you don't even need to use the built in OSX firewall.
2. Ditto for antivirus. You don't need to add anything. Just keep up with the software updates. Antivirus software will cause more problems (like slowness). Antivirus and Security software is more of a PC thing.
3. If you must have some antivirus software, then ClamXav works well and is free. But again, it's not necessary.
4. If you are really paranoid, and you want to completely control outgoing network activity, then look at Little Snitch, which will prevent apps and processes from "phoning home" without your permission. Again, unnecessary, unless you are pirating software.
5. Just be careful what attachments you open. Like an email from Nigeria, you can usually spot something fishy.
For many people, what some claim as common sense approaches to computing and security are often too much effort to always keep in mind, so security software can definitly help. If you feel you need security software then there are several titles that can work just fine. I recommend for now keeping things light so a free package like Sophos Home edition set to run on a schedule as opposed to anything performing on-access scanning and analysis should have negligable impact on the system. Most packages can be configured to do this.
Just be sure to set whatever anti-malware tool you use to be regularly updated.
Keep in mind these are just tools to help, and are not guarantees of complete security.
Dear Linc Davis:
I don't normally piggyback on someone else's question, but your thorough explanation is extremely helpful on this topic.
I'm hoping to get your advice on this issue, as I have never used a virus protection on any of my Mac over the years, however I am having to now install Parallels and Windows 7 onto a new Mac for work just simply to run Quickbooks (to be compatible with our global accountants all using the Windows 7 version of QB). I have never run Parallels before or any virtual machine, but need to know what I should do for virus protection on the Mac.
I am assuming I must still install something like Norton (what do you recommend?) on the Windows 7 VM, but am unsure if this will still protect the Mac or if I must do something else.
Windows 7 running in Parallels is not a threat to your Mac. You should have anti-virus software in that Windows system, but you don't have to worry about cross-contamination of your Mac system. Note that Norton is not a good choice on the Mac, and though I've got no experience with it in Windows, I've heard similar things about it there. As to what you should use in Windows, though, this isn't the ideal place to ask that question.
Thanks so much Thomas. This is mostly what I needed to know and make sure. I just don't want anything cross contaminating my Mac from any Windows stuff. Interestingly from everything I see on the Apple site on the PC side, the product of choice appears to be Microsoft Security Essentials (not Norton or any other 3rd party ware) - it's free and the Apple Discussion guys are all saying its the simplest, most effective and least intrusive of any of them.