Sabotage by an insider at a major utility facility, including a chemical or oil refinery, could provide al Qaeda with its best opportunity for the kind of massive Sept. 11 anniversary attack Osama bin Laden was planning, according to U.S. officials.
A new intelligence report from the Department of Homeland Security issued Tuesday, titled Insider Threat to Utilities, warns "violent extremists have, in fact, obtained insider positions," and that "outsiders have attempted to solicit utility-sector employees" for damaging physical and cyber attacks.
"Based on the reliable reporting of previous incidents, we have high confidence in our judgment that insiders and their actions pose a significant threat to the infrastructure and information systems of U.S. facilities," the bulletin reads in part. "Past events and reporting also provide high confidence in our judgment that insider information on sites, infrastructure, networks, and personnel is valuable to our adversaries and may increase the impact of any attack on the utilities infrastructure."
Watch the full report tonight on ABC News "World News With Diane Sawyer".
In the materials recovered after the Navy SEAL operation that killed Osama bin Laden in May, officials found evidence bin Laden sought to repeat the carnage of the Sept. 11, 2001, terror attacks on or around its ten year anniversary.
"The only way you can actually kill the large scale number of Americans that [bin Laden] literally was calculating was through the use of this critical infrastructure," Chad Sweet, former DHS chief of staff and co-founder of the Chertoff Group, told ABC News.
After gaining access to such sites, causing mayhem could be relatively easy, according to former White House counter-terrorism advisor and ABC News consultant Richard Clarke.
"There are a lot of very sensitive facilities where someone can get a job on the inside, get access to a control room, flip a switch, which causes an electric power grid to short circuit, causes a pipeline to explode," Clarke said.
The Department of Homeland Security said in a statement there was no specific threat.
"DHS routinely shares information with its state and local partners on a wide-range of potential threats, and as part of this responsibility, DHS issued an intelligence note to its federal, state, local, tribal and private sector partners on July 19 regarding potential threats to private sector utilities. While DHS has no specific, credible intelligence of an imminent threat posed to the private sector utilities, several recent incidents highlight the on-going threat to infrastructure in the utility sectors from insiders and outsiders seeking facility-specific information that might be exploited in an attack," DHS press secretary Matt Chandler said. "We will continue to work closely with our state and local partners, including our partners in the utility sector, to take steps to best protect from potential threats – including protecting our nation's infrastructure. This includes sharing information as well as best practices."
'I am Taking This Plant Hostage
U.S. officials were stunned last year in Yemen with the arrest of an alleged American recruit to al Qaeda, Sharif Mobley, of New Jersey, who had been employed as five different U.S. nuclear power plants in and around Pennsylvania after successfully passing federal background checks.
"If someone is determined, and has the right access, they could do damage that would affect thousands of lives," Sweet said.
Al Qaeda has already put out the word in its online magazine, Inspire, for "brothers of ours who have specialized expertise and those who work in sensitive locations that would offer them unique opportunities to wreak havoc on the enemies of Allah."
As evidence of American infrastructure vulnerabilities, the report specifically cites the attempted insider sabotage this April at a water treatment plant in Arizona.
Officials said then a disgruntled night shift worker took over the control room and tried to create a giant methane gas explosion.
"I am taking the plant hostage," the worker said in a recorded 911 call.
There was no tie to al Qaeda and his plot failed, but the incident was a reminder of how easily one insider could create potentially deadly mayhem.
"Facilities in the United States don't have to be attacked by terrorists with airplanes or bombs outside the facility," Clarke said.