File Viruses example essay topic

Most of us swap disks with friends and browse the Net looking for downloads. Rarely do we ever consider that we are also exchanging files with anyone and everyone who has ever handled them in the past. If that sounds like a warning about social diseases, its right along the same lines. Computer viruses are every bit as harmful and destructive, and come in a vast variety of types and strains. Computer viruses, can tear up your hard drive and bring down your system. However, unlike social diseases, computer viruses are almost always curable, and the cures for new strains are usually a matter of days away, rather than months or years.

A computer virus is a program designed to replicate and spread, generally with the victim being oblivious to its existence. Computer viruses spread by attaching themselves to other programs such as word processors or spreadsheets, or to the boot sector of the disk. When an infected file is activated, or when the computer is started from an infected disk, the virus itself is also activated. Many times a virus will lurk in a computers memory, waiting to infect the next program or disk that is activated. What makes viruses so dangerous is their ability to perform an event.

While some events are harmless like displaying a message on a certain date, and others annoying, like slowing performance or altering the screen display, some viruses can be disastrous by damaging files, and destroying data. Most viruses are created out of curiosity. There are those out there who create them out of malice, but far more of the creators are just meeting a challenge, to see if they can do it or not. A common type of virus would be a Trojan Horse, a destructive program disguised as a game, a utility, or an application.

When run a Trojan Horse does something harmful to the computer system, while appearing to do something useful. A worm is also a popular type of virus. A worm is a program that spreads itself across computers, usually by spawning copies of itself in each computer's memory. A worm might duplicate itself in one computers memory so often that it causes the computer to crash. A worm is introduced secretly into a host system either for fun, or with the intent to damage or destroy information. Now I will explain some of the more major viruses, and how they function.

FILE VIRUSES Most of the thousands of viruses known to exist are file viruses. They infect files by attaching themselves to a file that is executable, usually the. EXE and. COM files that control applications and programs.

The virus can insert its own code into any part of the file, misdirecting proper program execution so that it executes the virus code first, rather than the legitimate programs code. When the file is executed, the virus is executed first, infecting the system. Most file viruses store themselves in memory. There they can infect other programs as they are executed. A simple file virus will overwrite and destroy a host file, immediately alerting the user to a problem because the software they are trying to run will not work.

Because these viruses are immediately discovered they have less of an opportunity to spread. More dangerous file viruses can cause more subtle or delayed damage, and spread considerably before being detected. BOOT SECTOR / PARTITION TABLE VIRUSES There are only about 300 different boot sector viruses, but they make up for about 75 percent of all virus infections. Boot sector viruses include Stoned, the most common virus of all time, and Michelangelo, possibly the most notorious. These viruses are so prevalent because they are harder to detect, as they do not change a files size or slow performance, and are fairly invisible until their trigger event occurs, such as the reformatting of a hard disk. They also spread rapidly.

The boot sector virus infects floppy disks and hard disks by inserting itself into the boot sector of the disk, which contain codes that are executed during the system boot process. Booting from an infected floppy disk allows the virus to jump to the computers hard disk. The virus executes first and gains control of the system boot even before MS-DOS is loaded. Because the virus executes before the operating system is loaded, it is not MS-DOS specific and can infect any PC operating system: MS-DOS, Windows, OS/2, PC-NFS, or Windows NT. The virus goes into RAM, and infects every disk that is accessed until the computer is rebooted and the virus is removed from memory. Partition table viruses attack the hard disk partition table by moving it to a different sector, and replacing the original partition table with its own infectious code.

These viruses spread from the partition table to the boot sector of floppy disks as floppies are accessed. MULTI-PARTITE VIRUSES These viruses combine both the features of the file and boot sector / partition table viruses. They can infect any of these host software components. And while traditional boot sector viruses spread only from infected floppy disks, multi-partite viruses can spread with the ease of a file virus, but still insert an infection into a boot sector or partition table.

This makes them particularly difficult to destroy. TROJAN HORSES Like its namesake, the Trojan Horse virus usually masquerades as something desirable, such as a game or software program. The Trojan Horse generally does not replicate. It waits until its trigger event and then displays a message or destroys files or disks. Because it generally does not replicate, some researchers do not classify Trojan Horses as viruses, but I would think that any program that destroys data can be classified as a virus. FILE OVERWRITES These viruses infect files by linking themselves to a program, keeping the original code intact and adding themselves into as many files as possible.

Most file over writers may not be intended to do anything more than replicate but, even then they take up space and slow performance. And since file over writers, like most other viruses, are often flawed, they can inadvertently damage and destroy files. STEALTH VIRUSES Stealth viruses have special engineering that enables them to elude detection by traditional anti-virus tools. The stealth virus adds itself to a file or boot sector but, when you examine the host software, it appears normal and unchanged. The stealth virus does this by waiting in memory when its executed.

There it monitors and intercepts your system's MS-DOS calls. When the system seeks to open an infected file, the stealth virus races ahead and un infects the file and allows MS-DOS to open it, all appears normal. When MS-DOS closes the file the virus reverses these actions, reinfecting the file. Stealth viruses take up space, slow system performance, and can inadvertently or deliberately destroy data or files.

As you can see viruses are appalling and frustrating, and since viruses spread from one computer to another it only gets worse. Just like a contagious human virus which causes more harm as more people are infected. The same holds true to a computer virus infecting computers continuously. Viruses are, and always will be part of the computing world. They have been around since programming began, and will continue to thrive as long as computers are used. The bottom line is, that in today's world the only safe computer is one that isn't connected to the outside world.