Acts of cyberterrorism differ from acts of hacktivism in that their intentions or consequences involve more severe, permanent damage. This can include loss of life or economic collateral. Most of our sources suggest that cyberterrorism is not justifiable by freedom of speech. 
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Barry C. Collin of the Institute for Security and Intelligence describes the following hypothetical acts of cyberterrorism. While unlikely, each example illustrates the ways in which cyberterrorism goes beyond the boundaries of hacktivism.
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<li>"A CyberTerrorist will remotely access the processing control systems of a cereal manufacturer. change the levels of iron supplement, and sicken and kill the children of a nation enjoying their food."</li>
<li>"A CyberTerrorist will attack the next generation of air traffic control systems, and collide two large civilian aircraft. ...Much of the same can be done to the rail lines.</li>
<li>"A CyberTerrorist will remotely alter the formulas of medication at pharmaceutical manufacturers."</li>
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Mark Pollitt argues that cyberterrorist acts such as the ones above would be highly improbable because of the level of human involvement in each example: "Computers do not, at present, control sufficient physical processes, without human intervention, to pose a significant risk of terrorism in the classic sense." In the case of the cereal factory, for instance, Pollitt points out that the rapid depletion of the factory's iron supplies, as well as the change in taste of the cereal, would be immediately noticeable to the people working there.
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Nonetheless, some acts of cyberterrorism are successful, as is demonstrated by the examples of Anonymous and Stuxnet. Cyberterrorists indeed pose a threat to national security. It is therefore important for software systems performing critical tasks or guarding critical data to be thoroughly tested and made as close to impenetrable as possible.
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Click the links to the left to see historical examples of cyberterrorism.