Encyclopedia of Computer Science and Technology

242 information warfareShannon found that if as long as the actual data transmissionrate is less than the channel capacity C, an errorcorrectingcode can be devised to ensure that any desiredaccuracy rate is achieved (see error correction). A relatedformula can also be used to find the lowest transmissionpower needed given a specified amount of noise.The influence of Shannon and his disciples on computinghas been pervasive. Information theory provides thefundamental understanding needed for applications in datacompression, signal analysis, data communication, andcryptography—as well as problems in other fields such asthe analysis of genetic mutation or variation.Further ReadingCover, Thomas, and Joy A. Thomas. Elements of Information Theory.2nd ed. Hoboken, N.J.: Wiley, 2006.Gray, R. M. Entropy and Information Theory. New York: Springer,1990. Available online. URL: http://ee.stanford.edu/~gray/it.pdf. Accessed August 8, 2007.Hankerson, Darrel, Greg A. Harris, Jr., and Peter D. Johnson. Introductionto Information Theory and Data Compression. 2nd ed.Boca Raton, Fla.: CRC Press/Chapman & Hall, 2003.IEEE Information Theory Society. Available online. URL: http://www.itsoc.org/. Accessed August 8, 2007.Shannon, Claude. “A Mathematical Theory of Communication.”Bell System Technical Journal 27 (July, October 1948): 379–423, 523–656. Available online. URL: http://plan9.bell-labs.com/cm/ms/what/shannonday/shannon1948.pdf. AccessedAugust 8, 2007.information warfareInformation warfare has many aspects and can be foughton many levels. On the battlefield, it can involve collectingtactical or strategic intelligence and protecting one’s ownchannels of communication. Conversely, it can involve disruptingthe enemy’s means of communication, blocking theenemy’s intelligence gathering, spreading disinformation,and trying to disrupt their decision process. Beyond thebattlefield, media (including the Internet) can be used forpropaganda purposes.All of these objectives today involve the use of digitalinformation and communications systems. Examples include:• analysis of enemy communications using both automatictools and human analysts• cryptography and signal analysis• protection of computer and network infrastructure• attacks and disruptions on enemy information infrastructure,both military and civilian (such as denialof-serviceattacks on Web sites)• use of Web sites to spread disinformation or propagandaHistory and DevelopmentInformation warfare is as old as warfare itself, with suchthings as ruses designed to trick or confuse enemy sentriesor lighting many fires to convince the enemy that one’sarmy was much larger than in reality. Wiretapping andspoof messages began with the telegraph in the mid-19thcentury, and eavesdropping and other tricks with radiowere used in World War I. These arts had greatly increasedin scale and sophistication by World War II—an entire fakearmy corps was “created” to deceive the Germans prior tothe D-day invasion.Information warfare involving computers has been usedin recent conflicts. The active phase of the U.S. attack in thefirst Gulf War in 1991 began with systematic destructionand disruption of Iraqi information and command-and-controlassets through targeted attacks. As a result, the stilllargely intact Iraqi military was left blind as to the comingflank attack by U.S. forces.In 2007 a series of coordinated attacks by unknownparties paralyzed much of Estonia’s Web-based governmentand business structures following a dispute with Russia.To many observers this represents a model for “strategic”information warfare that might be used in future conflicts.(Note that the techniques used in information warfare bythe national military and the kinds of cyber attacks thatmight be favored by terrorists overlap. For the latter, seecyberterrorism.)Further ReadingArmistead, E. Leigh. Information Warfare: Separating Hype fromReality. Washington, D.C.: Potomac Books, 2007.Greenmeier, Larry. “Estonian ‘Cyber Riot’ Was Planned, but MastermindStill a Mystery.” InformationWeek, August 3, 2007.Available online. URL: http://www.informationweek.com/showArticle.jhtml?articleID=201202784. Accessed September23, 2007.Johnson, L. Scott. “Toward a Functional Model of InformationWarfare.” Available online. URL: http://bss.sfsu.edu/fischer/IR%20360/Readings/Information%20War.htm. Accessed September23, 2007.Libicki, Martin C. Conquest in Cyberspace: National Security andInformation Warfare. New York: Cambridge University Press,2007.Rattray, Gregory J. Strategic Warfare in Cyberspace. Cambridge,Mass.: MIT Press, 2001.Waltz, Edward. Information Warfare: Principles and Operations.Boston: Artech House, 1998.Input/Output (I/O)While the heart of a computer is its central processing unitor CPU (the part that actually “computes”), a computermust also have a “circulatory system” through which datamoves between the CPU, the main memory, input devices(such as a keyboard or mouse), output devices (such as aprinter), and mass storage devices (such as a hard or floppydisk drive). Input/Output or I/O processing is the generalterm for the management of this data flow (see also bus,parallel port, serial port, and usb).I/O processing can be categorized according to how arequest for data is initiated, what component controls theprocess, and how the data flows between devices. In mostearly computers the CPU was responsible for all I/O activities(see cpu). Under program control, the CPU initiated adata transfer, checked the status of the device (or area ofmemory) that would be sending or receiving the data, and