WHAT IS A COMPUTER VIRUS?
A computer virus is an unwanted program that invades your computer and, usually, results in problems which can range from a slowdown to making your computer unusable and irretrieveable destroying all files on your hard drive.
HOW DOES MY COMPUTER GET A VIRUS?
Back in the early days of computer viruses (viri?), before the internet and networks, viruses were spread by diskettes (aka floppy disks or floppies). Early anti-virus programs scanned all diskettes when you put them into the computer, and notified you whenever a virus was found, so that you would not copy that file, or files, onto your computer.
With the advent of the internet, blackhat hackers (not all hackers are bad) found a better way to spread their nasty creations. Although viruses can be still be spread from computer to computer via floppies and CDs that you receive or create, this is relatively uncommon nowadays.
HOW CAN I KEEP MALWARE OUT OF MY COMPUTER?
The bottom line is to use the best antivirus programs available. The most common ways that viruses now spread are through email, or downloading infected files from a website.
So how do you determine the best program. The first thing to do is research. Most antimalware testing appears to be done by magazines, although there are some independent labs that also do testing. AV-COMPARATIVES (www.av-comparatives.org)is an independent lab that performs anti-malware program testing exclusively. If you're interested, in seeing the results, go to www.av-comparatives.org. From there you can see a summary of test results by clicking on the Whole Product Dynamic Test link in the Latest Results panel on the web page.
But if you're not inclined to spend the time to do your own research, I'll give my recommendation for your consideration. Since the 2009 version came out in late 2008, my recommendation has been Norton Internet Security (NIS) becaust NIS is always at the top of the test results. It may not always be rated "first" but if you look at test results over time, it is always up there whereas other antivirus programs and internet security suites go up and down in the ratings.
Kaspereky Internet Security (www.kaspersky.com seems to continually get the highest scores in testing. Bit Defender (www.bitdefender.com is another frequently high-scoring internet security suite.
Free antivirus programs generally receive scores that are 10% or more below the top programs in testing. They are certainly better than no virus protection, but would you accept a flu or tetanus vaccine that was less than 90% effective? Also, there are very few free internet security suites available. Microsoft Security Essentials is a security suite that generally gets good reviews, although it is still noticeably less effective than Norton or Bit Defender suites.
KEEP YOUR VIRUS DEFINITIONS UPDATED
Anti-virus software publishers spend a lot of time researching viruses and keeping up on the latest variants. They publish updated virus definitions, usually about weekly. If you don't keep your virus definitions updated, the programs cannot protect you against the newest variants. Most anti-virus programs come with a 1 year subscription to their virus updating service. Where things fall apart is when users get too cheap to renew the contract, or don't bother to register their program. Without registering and having a current subscription, anti-virus programs cannot download the newest virus definitions, and cease to protect your computer.
Although backing up your data is an important security step, your CD or other media containing you backed-up data may have virus files on it and restoring your data after a particularly nasty virus trashes your computer, just puts the virus back on your computer. So pay a few bucks and make sure your anti-virus subscription is current.
When it comes time to renew your anti-virus program's subscription, if you shop carefully. Some clients have told me that they wait until a rebate is available and then buy the newest version of the software - complete with a 1-year subscription - for less than the cost of the annual subscription fee, after rebates. Keep your eyes and ears open.