An FBI bulletin says the warning is based on terrorist manuals and documents found at al Qaeda sites in Afghanistan. But the FBI says there is no intelligence that indicates such an attack is imminent.
Meanwhile, resource specialists are taking preemptive steps to make sure U.S. resources are well protected.
"Everyday, thousands of times a day, your water is being monitored for bacteria, chlorine levels, and for evidence of a terrorist attack," says Dave Rager, a director at the Cincinnati Water Works.
Bowers met with water works directors in Cincinnati to find out where the monitoring process begins, and how it is carried out. There, they start with the primary water source, which is the Ohio River.
Since Sept. 11, Rager's job has switched from defense—keeping the drinking water safe and clean—to offense: fighting off terrorist plots.
Rager says the public is probably unaware just how vulnerable the U.S. water systems really are.
Water and food are terrorist targets not only because people can't live without them but because disrupting the flow of the things we depend on could bring the country to a stand still.
Just down the river from Cincinnati's Water Works, researchers at the EPA's new National Homeland Security Research Center pour millions of dollars into detection devices in an effort to prevent just that sort of catastrophe.
Tim Oppelt, an EPA water specialist, says the agency puts sensors in bodies of water like Lake Michigan to detect toxins, comparing the sensors to devices used to measure chemicals in a backyard swimming pool.
Even fish are enlisted in the new war against water toxins, Oppelt says.
"For some contaminants [the fish] may cough, for some contaminants they may change their swimming and breathing patterns," he says.
But detecting contamination is only half the battle. Tracing it to its source is still close to impossible—-especially in the food supply.
Because the U.S. has no tracking system for its 90 million cattle, a disease like foot and mouth could wipe out hundreds of millions of dollars worth of livestock.
"I would put the food supply at a very high risk area," says Stephen Flynn of the Council on Foreign Relations.
Flynn says not being able to isolate the source of a deadly disease could mean economic catastrophe.
"We need to worry about everything that we value, because if we value them, then we now have adversaries who are looking to target them," says Flynn.
Dave Rager agrees. "It's kind of a cat and mouse game. You have to stay ahead of what the terrorists' knowledge is about science and technology and be one step ahead of them," he says.
Staying ahead will mean keeping the front lines ready— in the laboratories, on the ranches, and even along the waterfront.