This is because your computer can be attacked and infected by viruses through many ways.
Some of the common ways are:
- Email attachments.
Do you ever receive any email that looks like a rejected email that you have sent out? It usually comes with an attachment and in most cases it is a virus file.
- Corrupted Website.
Let's consider this condition.
You need some information urgently and you try to search it out from the Internet.
All in sudden you found that a site might be able to provide the answer.
You simply click and you found that is corrupted.
But at the same time, without your notice, your computer is corrupted too.
- Infected applications or documents.
Again you need an information or application urgently.
You found that a site can provide the answer.
You go there and download the files you want.
But when you open it, you computer is infected by viruses using macros inside the files.
There are many freebies you can get from the Internet.
Free games, applications, movies, songs etc.
But most of them are not as safe as you can imagine.
Many of them pretend to be a good content but in fact it is a spyware.
But if you are not, you are very dangerous and can be affected in just a second of so.
So install a security software is very important.