Understanding Viruses

Anyone with even a small amount of computer experience has heard of computer viruses. Even with no knowledge of how a virus functions, the word strikes fear into the heart of computer owners. What exactly is a virus and how does it function?

What is a Virus?

A virus is a computer program designed to enter your computer and tamper with your files without your knowledge. Once the program containing the virus is open, the activated virus can not only infect other programs and documents on your computer, it can duplicate and transmit itself to other computers that are connected to yours, just like a physical virus can move from one human host to another.

Viruses began in the late 1980s as personal computers and electronic bulletin boards became more common. Back then, operating systems, word processing programs and other programs were stored on floppy disks. Hidden viruses were programmed onto these disks; as the disks were transferred from person to person, the virus spread.

Who Creates Viruses?

Where do viruses come from? Every virus is created by an author with a different motive—but all virus builders feel their actions are justified. For some, a killer virus is the ultimate technical challenge, like climbing a mountain. For others, creating viruses is a form of self-expression. Some disgruntled employees, consumers or citizens turn to virus building as revenge for perceived injustices. And though it’s a frightening thought, some viruses are built and aimed by legitimate (but disreputable) businesses to weaken competitors. Other virus authors want to make their mark in Internet history; these writers get a thrill out of seeing their virus cause damage enough to attract news headlines both online and on the evening news.

What Do Viruses Do?

Today’s viruses are far more potent than the beginner versions we saw several decades ago. Viruses may be sent by opening email attachments, clicking on spam, visiting corrupt websites and links online, opening spreadsheets or even the original method—infected disks. But the Internet is now the superhighway for virus transmission.

Some aggressive viruses—such as the Melissa virus—automatically duplicate copies of itself to the first 50 people in your computer email address book. A frightening prospect—opening an email from someone you trust to be greeted by a virus, and that’s exactly what the author is counting on, your trust.

The damage caused by these viruses varies from minor delays in computer function to complete destruction of your hard drive. For companies, the price is far higher. A downed website can cost a company millions of dollars a day.

How does the virus infect your computer? Because floppy use is nearly extinct and the majority of CDs that change hands cannot be altered, you will most likely bump into a virus through online activity.

Some viruses attack your boot sector, the start up section of your hard drive. Other viruses infect executable program files, activating each time the program is started. The virus travels into the memory and further copies itself.

Macro-viruses are the most common type of computer virus. This type of virus attacks data files containing macros. Macros are lists of commands or actions found under key headings. The virus resembles a macro but when the file is opened, the virus is activated.

Multi-partite viruses are a combination of the boot sector and file virus. These begin in the boot sector and affect both your boot records and program files.