Another attempted terrorist attack on the United States in coming months is "certain" with al Qaeda remaining the top security threat to the country, according to the heads of major US intelligence agencies.
At the same time a growing cyber-security threat also must be addressed by the US intelligence community, the heads of the CIA, the FBI and other agencies told the Senate Intelligence Committee on Tuesday.
Asked by the committee's Democratic chair Dianne Feinstein of the likelihood of another attempted terror attack on the US in the next three to six months, the officials agreed with Director of National Intelligence Dennis Blair's initial answer of "certain."
While none of the intelligence chiefs, who included CIA Director Leon Panetta, FBI Director Robert Mueller and others, cited a specific pending threat, their testimony made clear that an evolving al Qaeda remains their top concern.
"My greatest concern, and what keeps me awake at night, is that al Qaeda and its terrorist allies and affiliates could very well attack the United States," Panetta said.
"Al Qaeda is adapting methods to make their plots more difficult to detect, shifting from large attacks with multiple players to using individuals without any background in terrorism, Panetta said.
Citing the Christmas Day attempt on a US airliner as an example, he said the suspect had a US visa but little history of involvement with terrorist groups.
"Obviously, they decided to make use of someone like that within a very short period of time" of the suspect coming into contact with al Qaeda, Panetta said.
In his written testimony to the committee, Blair said it would take the capture or deaths of al Qaeda's top two leaders-Osama bin Laden and Ayman al Zawahiri-to possibly end the group's intent to attack the United States.
On the cyber-security threat, Blair's written testimony described an inability to contend with attacks using computer networks and telecommunications systems.
"Sensitive information is stolen daily from both government and private sector networks, undermining confidence in our information systems, and in the very information these systems were intended to convey," Blair wrote.
"We often find persistent, unauthorised, and at times, unattributable presences on exploited networks, the hallmark of an unknown adversary intending to do far more than merely demonstrate skill or mock a vulnerability."