When several terrorist exploits are carried out concurrently or closely together to increase the degree of threat, panic, and/or death to targets. The coordinated attacks can involve a combination of land, air, and cyber attacks to produce maximum havoc.
To illustrate, the September 11, 2001, jetliner attacks on the World Trade Center and the Pentagon by terrorists—occurring within minutes of each other—produced a much more powerful fear inducer on the American targets with the multiplicity of attacks very close together than a single attack on one target would have caused.
With regard to computers, terrorist cells nowadays often employ the Internet to communicate with one another, to fill their coffers with money, and to gather intelligence on the designated enemy. Though there presently is no published evidence that the Internet itself has been targeted in a terrorist attack, malicious programs available on the Internet can allow those so inclined to attack networked computers having security vulnerabilities, bring the Internet to a halt, or attack a targeted nations’ critical infrastructures. Combined with conventional terror tactics such as bombings, terrorists could begin a coordinated and large-scale cyber attack against computers and networks supporting the United States’ or some other targeted country’s critical infrastructures, thus creating an Apocalypse. Because conducting such a large-scale, coordinated attack requires both financial resources and highly qualified personnel, security experts estimate that these kinds of advanced structured cyber attacks require anywhere from two to 10 years of planning and resource gathering.
Wilson, C. CRS Report for Congress: Computer Attack and Cyberterrorism: Vulnerabilities and Policy Issues for Congress. [Online, October 17, 2003.] CRS Report Website. http://www.fas.org/irp/crs/RL32114.pdf.