Virus

In computer language, virus is a computer program or a piece of code that can manipulate itself without the knowledge of the user. A virus might destroy your data on your HDD, make your computer performance slow and even spread itself to all your email contacts.

Virus can easily spread through email attachment, removeable media such as floppy disk or thumbdrive. virus can also be spread through downloading file on the internet.

The most common way to protect your computer being infected is to install an anti-virus software and update at least twice a week(i personally update everyday)and do not download email attachment if you don't know who is the sender.