As the war on terror continues to infiltrate the blogosphere, an increasing presence in the jihadi movement is a virtual terrorist who uses the nom de guerre Nemo.

Nemo — a name meaning "no one," taken from Jules Verne's "Twenty Thousand Leagues Under the Sea" — has compiled a comprehensive archive of virtual terrorist training manuals and posted them all online.

• Click here to see images from Nemo's Web sites and terror manuals.

In the past, many of these manuals and guidebooks, which contain hundreds of thousands of documents and offer would-be jihadis step-by-step guides on ways to hone their skills, were scattered across many Web sites and domains.

But Nemo regularly posts his findings among a network of some 25 radical bulletin boards, lobbying the Al Qaeda cause to select Internet users. He's now the ultimate "Jihobbyist," according to Jarret Brachman, a fellow with the Combating Terrorism Center at West Point.

"For Nemo, producing Al Qaeda propaganda has become a way of life," Brachman said. "He has compiled so much relevant, ideological material and made it so widely available, that thinking of him as a simple propagandist would be understating the contribution that he's made for groups like Al Qaeda."

Documents and videos posted online and reviewed by FOXNews.com give detailed instructions for:

— Firing rocket propelled grenades,

— Pinpointing the most vulnerable armor on military vehicles;

— Making improvised explosive devices (IEDs) and roadside bombs;

— Manufacturing explosives using household chemicals.

In one of Nemo's Web postings, FOXNews.com found a document, written in English, that describes the science behind building a nuclear bomb — how to detonate it, the damage done by various yields of uranium or plutonium, and when and how to attach fuses to the detonating charge.

Such information may help facilitate the production of a so-called "dirty bomb" — a weapon that combines radioactive material with conventional explosives, although Brachman said he doesn't see it as a viable how-to guide.

Of greater concern to Brachman is the possibility that Nemo will gain access and begin to pass around more potentially dangerous information.

“There are a lot more sophisticated treatments of the science behind weaponry available on private Web pages and academic journals,” he said.

Nemo doesn't limit himself to using the Internet as a storage facility for his training materials. There's evidence he is also advocating using the Web's commercial technology to plan attacks.

In July, the Washington-based Middle East Media Research Institute (MEMRI) found a message on a Jihadi bulleting board — apparently written by Nemo, using one of his aliases, "Ozooo" — in which he calls for terrorists to use mapping tools such as WikiMapia to identify and photograph strategic military installations.

Nemo included as an example a WikiMapia photo of a supposed NATO military base in the Middle East.

Not much is known about Nemo, an elusive, almost mythical character among intelligence operatives and the blogosphere. On some Web sites he uses a picture of the Nemo cartoon character to represent himself; at other times he posts a picture of a man in Arab headdress, his face partly obscured.

According to Jane's Security News, Nemo may be Palestinian, based on some of his clothing seen in pictures. He could be called Yousef and be in his early 20s, based on one of his e-mail addresses. There is reportedly some evidence that he has a young daughter.

"The masked photos that permeate his Web sites seem to be of himself — unless it's a security ploy," Brachman said. "What you tend to see with jihadist Internet propagandists is a combination of youthful rage and an intense ego complex. This guy really seems to have a high feeling of self-worth, a lot of time on his hands and a dark sense of humor. Beyond a rough sketch, there's not much more known about him in the open-source community."

Nemo is little known on English language sites catering to extremists views, but he seems to have found his niche among the Arabic-language sites and stealthily moves among their Web forums.

He is also reportedly building his own Web site, although the URL neither works nor gives any indication that it is under construction.

The threat posed by the relative ease of access to terrorist training manuals has not gone unnoticed by politicians, academics, the intelligence community or law enforcement agencies.

In November, the Homeland Security Subcommittee on Intelligence, Information Sharing and Terrorism Risk Assessment heard testimony about the online jihadi threat.

Information provided by Rita Katz and Josh Devon from the SITE (Search for International Terrorist Entities) Institute outlined the extent to which the virtual world is being used by terror groups to communicate, share information and avoid traditional meetings or training camps.

The SITE Institute experts also described a system of online message boards, protected by passwords, that jihadis use to talk to each other, often in code to avoid easy interception of details.

Experts say we've come a long way since the first online manual was posted. The first collated manual for terrorist training was said to be the "Encyclopedia of Jihad," written by mujahideen in Afghanistan during their guerrilla fight against the occupying Soviet military in the 1980s.

That manual, which was scanned and posted online, was of poor quality, but it has since been rewritten and published in the more Internet-friendly PDF format.

These days, virtual jihadis and "terror librarians" like Nemo are publishing much more sophisticated training manuals.

Many are posted online as videos, and show detailed instructions on how to make a particular weapon or explosive, or show an attack and its aftermath as proof that the weapon can be successfully used in the field against "enemy" targets.

The Web site postings maintained by Nemo highlight numerous short video clips. Many videos are already in the public domain, perhaps gathered from news footage or academic sources, but are often "hijacked" by the virtual jihadis with their own graphics, voiceovers and music.

For now, Nemo remains at large. He continues to expand his online library of training materials, his Web sites acting as a one-stop-shop for would-be terrorists. His identity remains unknown as he urges fellow terrorists to use the Internet and technological tools to aid their jihadi cause.

Brachman doesn't underestimate Nemo's importance for keeping "the wind in Al Qaeda's sails."

"It's guys like him," he says, "that help to keep the true believers hooked and help to bring the fence-sitters in."

Additional reporting by FOX News' Ghalib Tawfiq in Baghdad.