It has become fashionable these days to express skepticism about "cyber war"--and for good reason. The concept is ill defined; it has been used to describe everything from defacing websites to attacking critical infrastructure to committing espionage over computer networks. More troubling is that many of the heralds of cyber war have a commercial stake in the cyber security market. Some may have more ulterior motives for ramping up fears, such as a desire to fan the flames of Sino-American rivalry or to diminish privacy on the Internet.

But a troubling shift toward censorship, surveillance, and--yes--militarization in cyberspace is very real. Internet filtering is increasingly accepted worldwide, companies have imposed heavy-handed copyright controls, and surveillance in both the public and private sectors is widespread. Meanwhile, there are no international rules of engagement in this domain, and a burgeoning ecosystem of crime and espionage--cultivated by shadowy actors and state intelligence systems that stand to benefit--is ensnaring governments, civil society, and industry (see "Moore's Outlaws"). All this could soon generate a perfect storm. Individuals might withdraw from cyberspace altogether, gradually eroding the network effects that have benefited us for 20 years.

All armed conflict today invariably includes a cyberspace component: think of the 2006 Israel-Hezbollah war; the 2008 Russian-Georgian war over South Ossetia; the ongoing hostilities in Iraq, Afghanistan, and Somalia; and domestic hostilities in Burma, Tibet, Pakistan, and, most recently, Thailand (among numerous other places). Be it through kinetic strikes on the infrastructure of information and communications technology, missile attacks targeted with the aid of cellular geolocation, espionage that makes fraudulent use of social networks, or privateering that disables key computer networks at critical times, warfare has taken on this dimension because cyberspace is the strategic communications environment in which we all live.

Although invoking fears of an electronic Pearl Harbor may be overheated rhetoric, an arms race in cyberspace creates an environment in which crime, espionage, malware, denial of service, filtering, and surveillance prosper and thrive. In the rush to reject alarmism about cyber war, we should not lose sight of the very real geopolitical conflict that has insinuated itself into this domain and threatens to subvert its architecture. The militarization of cyberspace is not a fantasy but an urgent problem requiring immediate solutions.

Ronald Deibert is director of the Citizen Lab at the Munk school of global affairs at the University of Toronto.