The portion of the computer program that can be read, written, and modified by humans. A May 2005 crack attack exploiting some Cisco equipment powering the Internet once again fueled debate about whether the stolen Cisco Systems, Inc. code used to penetrate a supposedly very secure system poses a threat, in general, to the Internet. For years now, experts have been debating whether software having its source code freely distributed is less or more secure than proprietary applications. For example, the code for the Linux operating system is open source and available to all, whereas Microsoft Corporation’s Windows source code is proprietary information and is not readily available. The reported case fueling the debate involved a Swedish minor thought to have gained entry into sensitive aerospace and university systems at NASA’s Jet Propulsion Laboratory, the White Sands Missile Range, the University of California at Berkeley, and elsewhere. The teenaged cracker apparently used stolen source code from the operating system of Cisco routers to crack the highly secure TeraGrid, a supercomputing network. According to investigators, the cracker then gained access to 50 or more systems on the Internet. Cohn, M. How Dangerous Was the Cisco Code Theft? [Online, May 18, 2005.] CMP Media LLC Website. http://nwc.networkingpipeline.com/showArticle .jhtml?articleID=163105422.