Computer viruses are small software programs that are designed to spread from one computer to another and to interfere with computer operation.
A Trojan is a piece of software that works like a Trojan horse, masquerading as one thing to get inside a computer, and then attacking.
A virus attacks the host computer after slipping in through a hole in its operating system.
A worm works like a virus, exploiting flaws in operating systems, but it doesn’t attack once it breaks in.
A computer virus might corrupt or delete data on your computer, use your email program to spread itself to other computers, or even erase everything on your hard disk.
Computer viruses are often spread by attachments in email messages or instant messaging messages. That is why it is essential that you never open email attachments unless you know who it's from and you are expecting it. Viruses can be disguised as attachments of funny images, greeting cards, or audio and video files. Computer viruses also spread through downloads on the Internet. They can be hidden in illicit software or other files or programs you might download.
By Cynthia Hermida