Adm. Michael Rogers, who oversees the military's cyberspace operations, told the Senate Armed Services Committee that ISIS had "harnessed the power of the information arena" to propagate its ideology, recruit, move money and coordinate activity."
But he added that what concerns him the most is what happens when ISIS "starts to view cyber as a weapon system" to attack critical infrastructure in the U.S.
While Rogers acknowledged that ISIS had yet to demonstrate the skills needed to conduct such attacks, he said that "it would not be difficult" to achieve that capability.
"It's not beyond their ability if they made that decision," he said.
Rogers referenced the December cyberattack on the Ukrainian power grid
, which left hundreds of thousands of Ukrainians without electricity, as an example of the type of damage a cyberattack on critical infrastructure can cause.
He also expressed concern about traditional state actors like Russia and China, saying that unlike conventional military forces where the U.S. is dominant, "cyber is one area we have to acknowledge that we have peer competitors with every bit as much capacity and capability as we do."