Computer viruses are called "viruses" because they work a lot like biological viruses do -- passing from one host (machine) to another just as a biological virus passes from person to person.
And like their biological analogues, digital viruses replicate themselves and infect others (without the permission or knowledge of the user) by piggybacking on some kind of carrier.
The news media employ the term "virus" to describe several different types of electronic infections. The most common types:
•Virus - A small program, which can be benign or malicious, that is concealed within another program. Each time the carrier program runs, the virus runs, too, and has the chance to reproduce itself or wreak havoc.
•Worm - A small piece of malicious software that can grow exponentially through computer networks. Once it's on a computer, it scans the network for another machine with a specific security vulnerability. When it finds one, it exploits the weakness to copy itself to the new machine, and then starts replicating from there, as well. Worms require no user action to do their damage.
•Trojan Horse - A file that claims to be something desirable but is in fact malicious. It may claim to be a game or screen saver, for example, but instead does significant damage when you run it, such as erasing your hard drive. Trojan horses have no way to replicate automatically.
Many people don't realize that there is a proper way to use an anti-virus program. Just having anti-virus software loaded on your computer is not enough; you must keep the software up-to-date, run virus scans, quarantine files as needed, and renew your virus definitions file.
If you don't, you won't get the benefit of the anti-virus protection. If that sounds like a lot, don't panic: most modern anti-virus software allows you to automate most of the work.
Follow all of the steps below to get the most benefit from your anti-virus software:
Most computers come with at least a trial version of anti-virus software. Once the subscription runs out, though, you'll have to purchase a permanent one, or download a free anti-virus program of some kind.
There are many vendors who produce anti-virus software, and deciding which one to choose can be daunting. All anti-virus software performs the same function, so your decision may be driven by particular features like spyware and adware protection, availability, or price. Investigate what each product offers to see which one best meets your needs. Some of the more widely used anti-virus programs:
If you feel that your computer has been hacked or infected by a virus or worm, immediately disconnect it from the network or Internet (unplug the phone, DSL, or cable line) to keep it from getting worse or infecting others.
Then, use another, non-infected computer to download up-to-date anti-virus or anti-malware software and save it onto a portable memory device such as a CD, DVD, thumb drive or "memory key." Use the portable device to run the anti-virus program on the infected computer to clean up the problem.
Once you've done this, prevent re-infection by making sure your operating system is up-to-date and configuring your anti-virus, anti-spyware, and firewall software to automatically update and run constantly in the background.
ZoneAlarm Firewall (Free Version)
By now, most people know not to open email attachments that are from unfamiliar senders -- and even to use caution when opening email attachments from friends and family. If you are not expecting an attachment, ask before you open!
Beyond that, the best way to defend yourself from all electronic infections (besides using your anti-virus program effectively) is to keep your operating system and application software up-to-date with all security patches, and to back up critical data frequently.