"Dams, the power grid and other such infrastructure were once closed network systems. Then they were added to the Internet.
"We still thought of them as closed networks -- but they're not," said Lt. Gen. Edward Cardon, commander of U.S. Army Cyber Command and Second Army.
"Other systems touch them and that starts to create some problems," such as vulnerabilities to being hacked, he said.
Cardon spoke at the Army Cyber Institute and Palo Alto Networks-sponsored Joint Service Academy Cyber Security Summit, at the U.S. Military Academy, April 20 and 21.
It has been demonstrated that cars too, can be hacked, with each containing millions of lines of code, Cardon said.
In fact everything with lines of code on the Internet can be hacked and that's a problem for national security, he said."