That relatively brief timeframe only speaks to how quickly extremist groups have "optimized" the Web and developed a "highly evolved" process by which to develop terrorist networks, added Garry Reid, deputy assistant secretary of Defense for Special Operations and Combating Terrorism.

"Enabled by 21st-century technology, extremists have optimized the use of Internet chat rooms, Web sites and e-mail chains to spread their virulent messages and reach a global audience of potential recruits," Reid told the Senate Armed Services Committee in prepared testimony.

"It is this highly evolved radicalization process that enabled al Qaeda in the Arabian Peninsula to make contact with a wealthy Nigerian student living in London, recruit, train and equip him in the remote tribal regions of Yemen, position him in the Netherlands and ultimately dispatch him on a suicide mission to the United States, all within a period of weeks," Reid added.

"By contrast, the 9/11 operation took about two and a half years to develop from the time Osama bin Laden approved it in April 1999," he said.

Wednesday's hearing before the Senate Armed Services' Emerging Threats subcommittee arrives as federal prosecutors investigate how suspect Umar Farouk Abdulmutallab evaded airport security and almost detonated a bomb aboard Flight 253 over Detroit last year.

But it is not the only recent terrorist act or plot with roots traceable to the Web, according to federal officials.

A grand jury on Tuesday indicted Pennsylvania woman Colleen Renee LaRose — known in reports as "Jihad Jane" — for conspiring to commit terrorism abroad. LaRose was arrested last year for allegedly passing information to known terrorist groups, which she first contacted online.

Last year, federal investigators also discovered that Maj. Nidal Malik Hassan e-mailed an allegedly radical cleric in Yemen prior to killing 13 officers at the Fort Hood military base. However, intelligence officers reportedly knew about those exchanges before the attack.

Consequently, those testifying at Wednesday's hearing agreed that U.S. intelligence needed to pay more attention to those emerging threats online, identifying extremist networks and responding to those who pose an imminent risk to U.S. interests.

“If we can stop them upstream when they are becoming radicalized, then obviously we have an easier job of it than when they are downstream and they are getting into all kinds of dangerous activities,” said Ambassador Daniel Benjamin during prepared testimony.