Types of Computer Viruses

There are currently different types of computer viruses are available, each spread in a different ways. They are:

• Macro Viruses - Word processing documents can serve as sources of transmission for viruses that take advantage of the auto-execution macro capabilities in products such as Microsoft Word. Simply by opening an infected document, the virus, written in a product's macro language, can spread.

• Boot Sector Viruses - These viruses are spread by sharing diskettes between different computers. Any diskette can spread a boot sector virus, even if it is not a bootable system diskette. If the files are shared using sharing diskettes, boot sector viruses are spread to other computers, which then can infect other diskettes.

• Program - These viruses are spread by sharing program files. Because most users share programs less frequently than they share data or document files, this type of virus is less common than others. A program virus can infect other programs and damage data files on computer.

• Email or Hoax - These viruses are not really virus programs at all. They are email messages sent by well-meaning people to warn others about a new virus they read of. These false warning messages usually say "be sure to send this to everyone you know" and warn of major damage to computer or files. Hoax virus warnings can cause huge amounts of Internet traffic and unnecessary worry to others.

• File Infectors - These viruses attach themselves to regular programs, such as .COM or .EXE files under DOS. Thus, they are invoked each time the infected program is run.

• Cluster Infectors - They modify the file system so that they are run prior to other programs. Unlike file infectors, they do not actually attach themselves to programs.

• System Infectors - Computer operating systems typically set aside a portion of each disk for code to boot the computer. Under DOS, this section is called a boot sector on floppies or a master boot record (MBR) for hard disks. System infectors store themselves in this area and hence are invoked whenever the disk is used to boot the system.

Remember:

• A virus cannot appear on computer all by itself. The computer would have got it by sharing infected files or diskettes or by downloading infected files from the Internet.
• A write-protected diskette cannot become infected with a virus.
• A computer cannot get a virus by reading the body of a Pine email message, although one could be carried in a attachment (e.g. a Word or Excel file). These attachments should be scanned before reading them.