Photo: Luke Wolagiewicz/WPN; Kareem Raheem/Reuters

BOMB BUILDING 101: These Arabic-language Web sites offer how-to tips on constructing homemade explosives. The factual information is often sketchy, though.

In studying the behaviors of insurgencies in Iraq and elsewhere, as well as organized-crime syndicates and other groups, Robb noticed the many parallels to the open-source model in software. In addition to working in counterterrorism, he has also had a successful career as a software entrepreneur.

Groups like al-Qaeda resemble in some ways the classic insurgents of the past, such as the Palestine Liberation Organization, but several factors distinguish them from their predecessors, Robb says. For one, they aren't state-sponsored, which makes them harder to track down and eradicate. Being self-financed, they generate significant income from donations as well as from black-market commerce. Also, members of the group don't report to a central authority; they operate relatively autonomously, and they tend to be well educated, media-savvy, and comfortable operating in a globalized, high-tech world. And the use of information technology has given modern terrorists an operational edge their predecessors lacked.

Mimicking open-source developers, insurgent groups “hack at the source code of warfare,” Robb says. By that, he means they aren't bound by the traditional rules of military engagement; they use whatever works, with their tactics, techniques, and procedures all open to scrutiny and improvement by the community. Although such groups are weak by conventional military ­benchmarks—they'd clearly be outgunned and outmanned on an open battlefield—they can still threaten strong national militaries. That's because they don't aim to invade, hold, or govern territory, but rather to exert political influence by exhausting an adversary's capacity to fight back. Their preferred method of attack is to disrupt infrastructure, whether physical, financial, or political [see photos, “World at War”]. “System disruption is going to be the main thrust of warfare for quite a long time,” Robb predicts.

Rand CORP.'s Jackson has also studied terrorist organizations with an eye toward how they learn and share information—which he discussed in a recent report titled “Aptitude for Destruction.” Access to the Internet, Jackson says, has given such groups “a quantum leap in capability to get their message out.”

Many of the insurgent groups in Iraq, he notes, “are very Internet-savvy in terms of using it as an information-­dissemination medium.” The number of Web sites run by terrorists climbed from fewer than a dozen in 1997 to nearly 5000 in mid-2006, according to Gabriel Weimann, a professor of communications at the University of Haifa, in Israel, who has studied terrorism and the mass media. Not all of those sites pose a significant threat. Last year, a team of Pentagon analysts told Congress that of the thousands of jihadist sites they monitor, they closely watch fewer than 100—the ones they deem the most hostile.

Whereas the mass media used to control access to the public, Jackson says, insurgents now post videos and descriptions of their attacks online within hours of their occurrence, many of which are then picked up and replayed in the global media. Al‑Qaeda has a media affiliate that produces slick, branded video and audio files for online distribution. The videos are often encoded in multiple formats, so you can watch them on your cellphone or play them on a big-screen television. Some insurgents are even shooting in HDTV.

Terrorist Web sites serve not only to spread propaganda but also to share knowledge among insurgent groups, Jackson says. That helps explain why the learning cycles among Iraqi insurgents are some 20 times as fast as the Irish Republican Army's were in Northern Ireland in the 1980s, according to military estimates. The SITE Institute, a group in Washington, D.C., that monitors terrorist Web activities, has documented numerous cases of technical know-how being exchanged online. These include a slide presentation posted on a password-protected Arabic-language forum purporting to teach “beginner jihad fighters” how to rig a car bomb, as well as a training manual—linked to from various jihadist forums—that claims to cover explosives, poisons, and forgery, among other topics.

To be sure, the technical information that goes up on such sites is not always to be trusted, notes Michael Kenney, an assistant professor of public policy at Pennsylvania State University in Harrisburg. “Some of the terrorist instructional manuals and online chat rooms that have received so much attention in the press are, in fact, littered with basic mistakes,” Kenney says. He had one of the world's leading explosives experts review some online training manuals. The expert found that “for every four or five recipes, one may work, [but] only a trained eye can catch” the errors, Kenney says.