About Viruses

A virus is a program that is designed to adversely affect your computer, usually without your knowledge or permission. A virus implants itself in executable files on your computer and then spreads from one file to another. If a file is infected with a virus, or if you boot your computer from an infected diskette, the virus executes and can spread to other files or portions of the computer. As the virus spreads it will either corrupt your programs or just make a mess of your computer (like slow it down).

This range in effects of a virus is because there are two types of viruses: benign and malignant. While some viruses are benign and do not do serious damage to your computer, a great many are of the malignant type. A benign virus will for example at a set date or time, display some sort of message on the computer screen. On the other hand, a malignant virus can inflict significant damage your computer. This can result in the alteration of one of your programs so that it doesn't work properly (e.g., it may crash the program or cause it to insert incorrect information into your documents), it may slow down the speed of the computer, or in the worst case, affect a system area of your computer. Viruses which infect a system area (e.g., boot sector virus) may damage or delete files, cause the system to crash, or even erase your entire hard drive.

• Trojan Horse -- Also "Trojan". A program that may pretend to have, or is described as having, a set of useful or desirable features, but can actually cause some damage. Trojans are not technically viruses, since they do not replicate.
• Payload-- The payload code may cause text or graphics to appear on the screen, or it may cause corruption or erasure of data.
• Virus-- A software program that attaches itself to another program in computer memory or on a disk, and spreads from one program to another. Viruses can cause damage to data, make the computer crash, display messages, or lie dormant.
• Worm-- Not technically a virus, but can cause as much damage, is a program that is usually spread via e-mail or IRC/chat sessions.

• File infectors - These attach to or replace .com and .exe files on your computer. They can infect programs or all of the files in the directory with the infected files.
• Boot sector infectors - These viruses infect the boot sector of the computer. The boot sector contains information about the formatting of the computer drive (both hard drives and floppy disks have boot sectors). You can get a boot sector virus by booting the machine with an infected floppy disk in the drive. When the boot sector program is executed, the virus goes into memory and infects your hard drive.
• Master boot record infectors - The Master Boot Record (MBR) of the computer contains information about the physical layout of the hard drive and the location of the boot sectors of the drive. A virus may infect the MBR portion of the drive in a similar manner to boot sector viruses, from booting up the computer with an infected diskette in the drive.
• Macro virus - These are viruses that are common to Microsoft Word and Excel. Unlike other viruses, macro viruses do not infect programs but documents. A common macro virus is the Concept virus. Symptoms of this virus include: when you try to save a document, Word only lets you save the document as a template; or the file icon looks like a template icon, instead of a document. Microsoft provides a protection utility called ScanProt that is installed in Word and which can scan all Word files as you open them.

  Note: The Concept macro virus can infect Word files on both Windows (3.x and 95) and Macintosh machines. The Macro virus in Excel is called ExcelMacro/Laroux. It is a non-destructive, non-harmful macro virus. Microsoft provides a tool called XLSCAN97 to detect and remove the macro virus from files.

Undoubtedly you have seen email messages that purport to warn you against viruses that are spread through email messages and warn you against opening messages with certain subjects headers (e.g., Do not read or open any e-mail titled Good Times! It will destroy your computer!). You cannot get a computer virus simply by reading an email message. However, you can get a virus from an attachment that comes with an email message. Attachments may be virus files or the attachment itself may be infected (i.e., a Word document with the Macro Virus).

• Receiving an e-mail with a file attached to it that contains a virus. Once the file is open, your computer will become infected. Go here for some examples.
• Downloading a file from the internet that contains a virus. Once you run it, your computer will become infected.
• Viruses are also transmitted by computer networks (2 or more computers linked up together) and by infected disks. Do not use someone else's floppy without virus-checking it first.
• If you boot a computer with a floppy infected with a virus (boot virus), your computer will be infected. It's not advisable to boot your computer using a floppy.

Your risk for getting a computer virus depends on your computer use. You are likely to get a computer virus if you use a floppy disk on several different computers. If you are the only person to use your computer, and do not receive files from other people and are not connected to the Internet, you probably will not get a virus. However for example, if you download library searches while working at one of the library Sparta stations and then take that diskette to a computer in a public or a department's computer lab, and then take the diskette to your computer at home, there is a good chance you will pick up a virus along the way. If you receive e-mail attachments from many people and open them even if you do not know the sender, you are more than likely to acquire a computer virus.

Because viruses are most often designed to be deceptive, you can never be sure that you have not picked up a virus from someone else's computer. The best way to protect yourself and your computer is to buy and install anti-virus software, especially one that can scan all floppy diskettes you use. Also, once you have the anti-virus software running, make sure to update the virus profiles according to the instructions for your particular anti-virus software package.