Computer viruses are malignant software that is designed to affect the functions of the computer that it is downloaded into and it can be derived from, or transported through, information technology (IT) networks and storage media such as USB sticks, CDs, and others. The term was coined by Leonard Adleman, a computer specialist and molecular biology expert who saw a distinct similarity with how a computer virus works with that of its biological counterpart. You must remember that the term "virus" is not a catch-all phrase for malware in general. They are different from computer worms in that they directly attack the very system of the computer, while worms merely multiply by themselves and be distributed while leaving the original program intact. Fortunately, a free antivirus download can easily deal with the problem, but sometimes your PC can be so infected that you need to reinstall the OS altogether.
Such is the prevalence and nature of computer viruses that it is projected by Sophos that they number around 95,000, although according to the WildList Organization, only a thousand or more are active these days given the fact that antivirus companies do tend to overestimate their cleaning capabilities. A greater part of this number is dedicated to attack Windows-based computers, most of which can be remedied simply with a free antivirus download. Some are made to infect other OS platforms such as Linux and Unix but they are very rare. Other programs such as OS/2 and Netware that offer less tempting targets for viruses and FreeBSD which are primarily designed on security see less frequent attacks.
However, recently there has been an increase in infections to newer programs such as the Mac OS 9. Whatever the OS and kind of virus that is involved, these malware are often incurred by computer enthusiasts who unwittingly download them into their PCs or laptops, and most cause havoc to the OS program that was originally running smoothly. But this is not the case with Core War, a pioneering program developed and used in Bell Laboratories in 1970 and considered to be the prototype of the computer virus. It has all the hallmarks of virus programming: Core War instructs the OS to hunt and take down other programs other than its own while protecting itself and its copies from retaliatory attempts from hostile programs. It can replicate, regenerate, transfer from one memory area to another, and get rid of opposing software by taking them to less friendly areas. The program that has the most surviving number of replicates wins. This breakthrough was followed by a computer application that was published by the "Scientific American" in 1984 explaining in detail how to create smaller-sized programs that can directly affect their hosts; this in turn was superseded by the "Brain" virus program created for the ARPANET in 1986, which is noted for the tongue-in-cheek inclusion of the virus programmers' own personal details within its source code.
A virus is created to integrate itself within the host program. It will be activated once that program is run or through a set timetable and will cause any number of actions such as displaying an innocuous message to the gradual degeneration of the host computer's functions to the total deletion of every critical data in the computer. One type of virus is the so-called "logic bomb" that replaces the boot-up program with one of its own; it generally does not do any harm to the computer itself. Another type is the macro virus that affects the macros generated in Microsoft Office programs. Both types can be easily dealt with a paid or free antivirus download. With the popularity of the Internet came the ever-increasing threat and spread of modern computer viruses. However, the trend still appears to affect only those computers installed with Windows; other systems that are less popular such as those based upon UNIX seemingly are less at risk.
When a new virus is discovered, its naming follows a convention that gives it a specific term. Dealing with them has been the task of many antivirus companies for some years now. Be they free or paid antivirus programs, they try to get rid of viruses through three ways: Attempt to recover damaged files by taking off the viral program, quarantine or isolate offending files for future recovery and so that they cannot harm unaffected files, and erase affected files. Increasingly, antivirus companies have banded together to work towards the prevention and spreading of new viruses.
It always pays to be informed when dealing with computer viruses. And with the right tools such as a paid or free antivirus download to help you out, you can be sure that you can keep your computer secure from them.