Viruses, Worms, Trojans and Cookies
Most computer users consider anything that invades their computer as a virus but in actuality it may be a virus, a worm, a Trojan Horse or a combination of the above. A computer "bug" is not a virus. A bug is a problem that occurs due to a problem within the computer system itself.
A virus is a malicious program that attacks programs, data or on some cases hardware in your computer. The usual method of entry into your computer is by email as an attachment. It usually arrives an executable file (the last part of the file name will be .exe) and when you run the file (or open the attachment), it does it's dirty work.
A worm usually arrives as an email also, in fact, as you will see, the friend may not actually have sent the email. A worm, unlike the virus, does not attack the programs or hardware. It will replicate itself and multiply so that it consumes a computer's resources so that it slows to a crawl and sometimes shuts the computer down. The worm will also attack your email directory and mail itself out to everyone in your directory, infect those computers and continue mailing itself on and on.
The Trojan Horse gets into your computer because you brought it in (hence the name). I will give you an example of a Trojan. There are programs on the Internet that promise to speed your system up or otherwise improve your computer for free. If it sounds too good to be true, it is. Some of these programs are actually Trojan Horses. You invite them into your computer to do one thing, but they accomplish something entirely different (good for them, bad for you). Unlike viruses, Trojans do not infect other files nor do they multiply like worms. Some Trojans open a back door into a computer so control can be seized by another computer.
The best prevention against all malware is to have an up to date virus program installed on your computer. You should have regular updates and should scan your computer on a regular basis. If you can't stand spending the $40 - $50 annually to maintain a virus program, see page seven of this web site to obtain a free one. A simple safeguard against a worm is to put an entry in your address book with yourself as the recipient. I use the name of "Alert", with my own email address as the recipient. If a worm gets into your computer and starts mailing itself to everyone on the email list, it will also send you one with the sender name of "Alert". You can then take action to rid your computer of the pest. The best solution to prevention of a Trojan Horse is to NEVER open a program unless you are absolutely sure that it is safe.
Here is a tip that may save you from a exasperating problem. The person involved bought a new computer which came with a 90 day free trial virus program already installed. When they signed up for Internet access, they chose AOL and received a virus program as part of the package. the computer became very slow and suffered from continual system lock ups. Two different virus programs on the same computer do not coexist well at all. They both struggle for control and your computer will suffer from many problems, a total system lock up being one of them. Before installing any new virus program, delete the old one no matter how old it is. See how to properly delete a program on page seven of this web site.
Many soldiers in combat are killed or injured by "friendly fire", that is accidental fire from their own troops. Unfortunately, some of our computer problems are caused by "friendly" fire also. That is to say, legitimate computer programs on our computers that tend to take over and hog the computer's resources so badly that they might as well be malware. I refuse to use two of the popular audio programs because of their tendency to do just that. I won't name any names (can we say lawsuit?), but I am content to use Windows Media Player for my music needs. Your needs may vary from mine. I also hate programs that keep insisting I upgrade to a better version for only $$$ (but that's another story). I would suggest that you only make one change to your computer at a time. Do the change (or installation), use the computer for a few days to see how it reacts, then do another. This way you can better isolate what caused the problem if one crops up.
Cookies are small programs that a computer site places on your computer so it may communicate with your computer easier. If you visit a site that requires you sign in with a password, that site may place a cookie on your computer to identify you so you do not have to sign back in continually. Cookies are usually harmless and you may delete them if you wish by going to the tools section of Internet Explorer.