Once upon a time, Apple even used the lack of viruses as a marketing tool to sell more Macs. In a company marketing web page titled, "Why You'll Love a Mac" (no longer exists) the language was once quite clear, "Apple's OS X doesn't get PC viruses." Somewhere around 2012, that message changed to "It's built to be safe."\u00a0\u00a0The update itself happened shortly after nearly 600,000 Macs were infected with a trojan named "Flashback," and although this wasn't the first time Macs were targeted, it was certainly the largest. This security breach led Apple, and Mac users, to understand that they were in no means immune to viruses or malware. If you prefer to stick to your iPhone or iPad, you should also read our review of the WinX MediaTrans iPhone\/iPad manager.\r\n\r\nWhile large scale viruses are still a rarity among Mac users, that doesn't lessen the need for smart antivirus software in order to help you recognize, and react to possible infections. Here are five smart (and free) choices to keep your machine free from viruses and malware. With your Mac protected, it will be safe to download things like the Moosejaw X-ray app.\r\n1. Sophos\r\nSophos Antivirus features an easy to use interface that can be used for custom on-demand scanning, as well as fully automated scans at user-defined intervals. The software runs quietly in the background and is surprisingly resource friendly so it doesn't slow down your system as much as some other options. With the "Live Antivirus" feature, Sophos even updates your software the moment that new threats are found online, and through use of the\u00a0link scanner, it's now possible to perform full scans on web pages before you click the link to visit.\r\n\r\nIn a head-to-head test of several popular free and paid options for Mac, Sophos was the clear cut winner, and one of only two to achieve a perfect 100-percent in catching all malware it was tested against with zero false positives.\u00a0 With these stats, it wouldn't be a reach to call Sophos the best antivirus software on our list.\r\n\r\nBest for: Everyone\r\n\r\nGet Sophos\r\n\r\n\r\n\r\n \r\n2. Avast!\r\nAvast! is widely considered the best (or near the top) in terms of free Windows antivirus software. For the Mac, the system certainly doesn't disappoint, and it's definitely on par with the top choice, Sophos. The one major drawback to Avast (on Mac) is that it only scans for Mac-specific malware, which is fine if you never use a Windows-based PC, but becomes problematic in terms of email and file sharing when you're sharing these files outside of a Mac-based ecosystem. As far as security on a Mac though, Avast! is about as good as they come. In fact, AV Comparatives tested Avast and found that it detected 100-percent of the malware that they attempted to download to the system, which makes it the only other Mac antivirus software with that distinction (Sophos is the other). With Avast, you're safe to download the best personal finance software for Mac.\r\n\r\nBest for: People in all-Mac ecosystems, or those that prefer it to Sophos.\r\n\r\nGet Avast\r\n\r\n\r\n\r\n\r\n\r\n\r\n3. ClamXav 2\r\nClamXav 2 uses the open source ClamAV virus scanning engine to scan for both Windows and OS X malware, viruses, and badware.\u00a0ClamXav is actually the most lightweight free antivirus software in our recommendations, and it's compatible with any Mac running OS X 10.5 or higher.\r\n\r\nThe only real drawbacks to ClamXav 2 is the frequency in which virus and malware definitions are updated. It seems to be the slowest at updating the database of any of the five we've tested.\r\n\r\nBest for: Multi-taskers or those that want a lightweight option that runs smoothly in the background with minimal interruption.\r\n\r\nGet ClamXav 2\r\n4. Comodo\r\nComodo is an extremely powerful antivirus software, but its strongest point also makes it a relatively unpopular option outside of the website administrator crowd. While its scoring on malware blocking tests and built in sandbox for opening packages and files from unknown sources makes it a very safe and secure utility, the nuts and bolts of the program are decidedly expert-only, and better left to those who really know that they're doing.\r\n\r\nAs far as an out-of-the-box option, Comodo is powerful, but it had relatively poor scores in blocking malicious URLs, the rate of false positives is high (identifying safe software as malware), and the previously mentioned sandbox tool makes it a real pain to install some legit software. For example, when installing Sketch 3, I had a heck of a time getting the antivirus to understand that the package was safe, and that I did indeed want to move it to my Applications folder.\r\n\r\nBest for: The IT crowd that likes to tinker and determine exactly what they want a program to do. High tech\u00a0IQ is required for best use of the administrator tools.\r\n\r\nGet Comodo\r\n\r\n\r\n\r\n \r\n5. Avira\r\nAvira is a utility that was once (according to\u00a0AV Comparative testing) on par with Sophos and Avast in the sense that it caught 100-percent of malware tested. In the latest test, it caught 91-percent, making it an admirable contender, but putting it in the decidedly second tier category of some lesser-knowns such as ClamXav 2. That said, Avira is by far the most user friendly of any of the antivirus programs tested, and it would make a perfect addition for the non-tech demographic, such as your parents or grandparents.\r\n\r\nBest for: Your parents, or anyone that needs a program that runs with minimal intervention or know-how.\r\n\r\nGet Avira\r\n\r\n\r\n\r\n \r\n\r\nAs far as what that means for you, well it really depends on what you're looking for. Each application offers different benefits,\u00a0so your best bet is to determine what type of user you are, and begin testing the options from there.