introduction to viruses

Most people are aware of threats to their computers. Viruses, Worms and Trojans have become so common that new stories about computer threats appear daily in newspapers and on television. However, you may not realise is that these threats are relatively new. Two things have happened in recent years to make computer threats possible:
-Computers became affordable and therefore common
-The Internet allowed computers to connect easily to each other

This software was the first to copy itself from computer to computer, infecting all the machines it came in contact with.

Some people think that only PCs (IBM clones) are at threat and that Apple Macintosh (Mac) and Unix/Linux systems are immune to threats such as viruses. This is not entirely true. Other computers systems are often more secure than PCs. However, the main reason that more PCs are affected by viruses is simply that there are more PCs in the world.