ISTANBUL, Turkey — In December, Al Qaeda operatives posted a manifesto on the Internet calling for attacks inside countries allied with the United States in Iraq. Spain, with elections approaching, was singled out as a target.
On March 11, terrorists set off bombs on four commuter trains in Madrid and killed 191 people. Three days later, Spanish voters replaced the pro-war government with a party whose leader had promised to withdraw the country's 1,300 troops from Iraq.
The posting of the strategy and the timing of the Madrid bombings shocked even the most hardened Al Qaeda watchers recently when they reviewed the little-known manifesto.
"It's quite extraordinary in that you have a group of people ... talking about influencing a political process and then having it happen," said a U.S. national security official who analyzed the 54-page posting and spoke on condition that his name not be used. "Reading through this thing, it is just mind-blowing."
Since Osama bin Laden and his followers were driven from their bases in Afghanistan, the Al Qaeda terrorist network has demonstrated an increasing ability to exploit the Internet as it reconfigures itself as a semi-leaderless global extremist movement far more elusive than the original incarnation.
Websites run by Al Qaeda and its backers have become virtual classrooms for terrorists, offering instructions for activities such as kidnapping and using cellphones to set off bombs, like the ones used in Madrid. Independent Al Qaeda cells and the network's loose hierarchy use easily available encoding programs and simple techniques to exchange virtually undetectable messages between Internet cafes in Karachi and libraries in London.
The Internet's importance to Al Qaeda was highlighted this month by the disclosure that Pakistani authorities had apprehended Mohammed Naeem Noor Khan, a suspected Al Qaeda computer engineer, and collected a wealth of electronic material.
E-mail and other information from Khan's computers led to the arrests of 13 suspects in Britain and sent investigators scrambling to unravel electronic links among militants in Pakistan, Europe and the United States, British, U.S., and Pakistani authorities said. The discovery of files on financial institutions in New York and Washington among Khan's trove also played a role in prompting the Bush administration to issue a terrorist warning.
Although it has long been known that Al Qaeda used the Internet to conduct reconnaissance on potential U.S. targets, the disks and hard drives taken from Khan disclose much about the resiliency and adaptability of a far-flung network hiding in plain sight, said U.S. and foreign intelligence officials and outside experts interviewed for this report.
"The Internet allows the organization to become a virtual self-perpetuating and changing entity in cyberspace that provides technological guidance and moral inspiration to a new generation," said Magnus Ranstorp, a counter-terrorism expert at the University of St. Andrews in Scotland.
Rather than the computer whizzes often described by government officials and the press, the Al Qaeda operatives are more often people with everyday skills who have harnessed the Internet in a campaign against the United States and its allies. Even Khan, whom senior U.S. officials describe as extremely computer savvy, used skills available to many people with computer training.
Over time, they developed and shared techniques to avoid detection. An Al Qaeda survival manual warned adherents not to use the same Internet cafe too many times. Messages should be written on a word processor and pasted into an e-mail to avoid keeping the computer connected to the Internet for too long, it said.
The result is a changing definition not only of Al Qaeda but also of the threat from what is known as cyber-terrorism. After Sept. 11, the biggest fear of terrorists using the Internet was their potential to disable air traffic control systems or disrupt the electric power grid of the United States. Billions were spent shoring up infrastructure defense.
Although those concerns remain, authorities said no incident of cyber-terrorism has been recorded and worries have receded.
Instead, the discovery of the December manifesto, the arrest in Pakistan last month and the accumulation of other evidence are leading to recognition that for now, at least, cyberspace is not a weapon for Al Qaeda, but a tool -- one more difficult to counter than gunmen huddled in caves and tents.
James Lewis, director of technology policy at the Center for Strategic and International Studies in Washington, said one clear advantage for Al Qaeda is that the Internet gives it a communications system that rivals that of a superpower without the accompanying risk.
"There is no central headquarters," he said. "There is no central place you can knock out."