Addressing a Washington Post conference Thursday, Napolitano cautioned the number of cyberattacks on financial systems, transportation and other networks is growing and have the potential to cause deaths and economic consequences.
She warned cyber assaults had come close to crashing some key infrastructure.
"It could theoretically cause a loss of life, but also a huge economic loss," she said. "We've seen attempts on Wall Street, transportation systems, things of those sorts."
Politico said comprehensive legislation covering cybersecurity has been working its way through the U.S. Senate for more than a year, but may not reach the floor this legislative session.
However, Napolitano said Congress is aware of the importance of cyber threats.
"If there's any area of international concern that the Congress is going to move on this session, it's going to be cyber," she said.
"One of the problems we have is that the current international regime, international law, international rules of conflict … really have not developed with cyber," she said.