Remember that most of the time you are using the Internet, whether it's receiving email or accessing a Web page, you are taking files from one computer and allowing them onto yours. Some of those files may be infected by viruses, which are the most prominent technological danger on the Internet.
Viruses are small programs that people write with the hope of causing trouble.
Although some are just pranks or stunts, most are designed to intentionally damage or destroy your files or computer. It's pure vandalism, and viruses can cause especially big trouble because they are often written to exploit your connection to the Internet, spreading themselves automatically to infect other computers. Only download software and files from reliable sites, such as the those of large, established companies, which usually check programs thoroughly before making them available for download. Be careful of opening any files that are attached to your emails, especially from people you don't know. It can sometimes be difficult to identify an executable file, but it helps to understand the concept of file formats and extensions .