The Cold War is Over. The Cyber War has Begun.

Contemplating Russian nuclear threats during the Cold War, the strategist Herman Kahn calibrated a macabre ladder of escalation, with 44 rungs ranging from “Ostensible Crisis” to “Spasm or Insensate War.”

In the era of cyberwarfare that’s now dawning, the rules of the game haven’t yet been established with such coldblooded precision. That’s why this period of Russian-American relations is so tricky. The strategic framework that could provide stability hasn’t been set.

Russian hackers appear to be pushing the limits. In recent weeks, the apparent targets have included the electronic files of the Democratic National Committee, the private emails of former secretary of state Colin Powell, and personal drug-testing information about top U.S. athletes.

The Obama administration is considering how to respond. As in most strategic debates, there’s a split between hawks and doves. But there’s a recognition across the U.S. government that the current situation, in which information is stolen electronically and then leaked to damage and destabilize U.S. targets, is unacceptable.

“A line has been crossed. The hard part is knowing how to respond effectively,” argues one U.S. official. Retaliating in kind may not be wise for a country that is far more dependent on its digital infrastructure than is Russia. But unless some clear signal is sent, there’s a danger that malicious hacking and disclosure of information could become the norm.

The Cold War is over. The Cyber War has begun.