Everything that can be used for good can be equally used for evil. A hammer, in the hands of a carpenter, will be part of a tool set that results in remarkably useful furniture. The same tool, in the hands of a criminal, is a way to break into homes. The same applies to technology, particularly computers. For the average Joe, it could be a means of entertainment and productivity, but for the malicious programmer, the same computer is a means of disrupting the status quo. This is where viruses come in. Manufactured by individuals who have (usually) nothing to gain from them, viruses have had a crippling effect on businesses and individuals worldwide.
As a result, anti-virus companies have swept in the save the day by offering a means of protection. Today, there are many anti-virus products on the market, whereas in the past, only two were popular: Norton and McAfee. While these two have maintained a dominant foothold in the market, the options available are now immense and the appropriate anti-virus for you may simply depend on which OS you use and what features you need. All anti-virus programs that are kept current have a fairly comparable dictionary of viruses that they use for your protection that can be updated regularly at your discretion, so that isn’t a deciding feature. Both McAfee and Norton are available for Windows, Mac, FreeBSD, Linux, and Unix environments (which is a rare feature of antivirus suites). This also applies to BitDefender, Clam, Kaspersky, and Sophos (among others). One notable aspect that differentiates Clam from the remainder, however, is that it is distributed under the GNU General Public License. This means that, for the average user, the software is free to use. The choice of which product to get, of course, is entirely yours!