They neither carry weapons nor lay ambushes for soldiers in Iraq or Afghanistan. But thousands of radical Islamists are waging a different kind of war from behind their computers, called "electronic Jihad."
These radical Islamic sites have sprung up over the past few years, specializing in the organization and coordination of concerted cyber-attacks against Israeli, US, Catholic and Danish Web sites.
All you need to join this anonymous cyberworld is an address registered in Iraq or in tribal zones in Pakistan, and basic computer savvy to carry out attacks in which "internauts" from the four corners of the world take part.
Among their most high-profile attacks to date was that on the Danish Internet site of daily newspaper Jyllands-Posten which published caricatures of the Prophet Mohammed in September of last year that sparked violence among Muslims worldwide, albeit a few months later.
"It is the Internet version of jihad. You can telecharge viruses which will be activated at the planned date. I downloaded one which was called `jihad reminder,'" said Anne Giudicelli, a French specialist who runs a "terrorism" consultancy monitoring radical Islamic Web sites.
A recent report from the US-based Jamestown Foundation -- a group that aims to inform policymakers about countries of strategic and tactical importance that might restrict access to such information -- highlights a so-called electronic jihad Web site (http://www.al-jinan.org), where the "electronic jihad program 1.5, silver edition virus" is available.
It also offers to install a toolbar on your personal computer that connects and then automatically brings up back dates, times and targets of cyber attacks.
"In the radical Islamist forums, you find sections that are the electronic jihad equivalent of how to make bombs," Giudicelli said. "How to cyberattack: That has become part of the jihadist's basic training."
Jean-Pierre Filiu, a professor in political science at Paris' Institut d'Etudes Politiques and author of the book Les Frontieres du Jihad (The Boundaries of Jihad) described the developments as "an impressive jihadization of the Islamic landscape."
"Ten years ago, friends and I would find videos made in Chechnya or in Algeria, which were generally rather gory," he said. "Today we are finding on the Web things which are at least as obscene in terms of violence, but which have a major distribution."
Established in 2003, the Global Islamic Media Front offers some 500 films for download, he said.
"There is no doubt a second layer, accessible only to the converted with sophisticated passwords, but this first layer, which is totally open on the network, must already be arousing interest, feeding and circulating propaganda, whose devastating impact we have trouble assessing in the West," he said.
Many forums, whether openly Islamic or managed by Arab media like Al-Jazeera, raise the idea of cyber-attacks.
During the uproar in September over Pope Benedict XVI's remarks about Islam, an Internet piracy campaign targeted the Vatican's Web site, but it was reportedly little affected due to its high level of protection.
Thomas Hegghammer, an expert at the Norwegian Defence Research Establishment in Oslo, however, played down the threat.
"Taking down a Web site is not a big problem," he said.
"So far there has been no example of cyber-attacks that have caused physical damage. There have been a number of cases where Islamist hackers have taken down Web sites, particularly in Israel and elsewhere, but none of this has caused physical damage or serious disruptions," he said.