The U.S. must respond to Russia’s hacking. The question is how.

The headlines about the hacking of our election have only begun to blare. Monday morning, Senate Majority Leader Mitch McConnell joined the bipartisan chorus calling for an investigation, which will likely follow the U.S. intelligence community’s own “full review,” ordered by President Obama to be finished before Inauguration Day. At this point, everyone but the president-elect and some of his entourage accepts that the Russian government directed the hacking, either to undermine the election or—in the CIA’s latest estimate—to help Donald Trump win.

Before we plunge too deeply into this tale, straight out of a Cold War movie, it’s worth reviewing some context: How long has this sort of thing been going on? How is this hack different from all other hacks? How shocking is it? And what can President Obama (or, if he ever snaps out of his denial, soon-to-be-President Trump) do about it?

First, nations have been hacking into each other’s computer networks for a long time. Back in 1967, when the ARPAnet, the military’s precursor to the internet, was about to roll out, a few computer scientists warned that putting information on a network—where it can be accessed online from multiple, unsecured locations—creates inherent vulnerabilities; keeping secrets, they warned, will be very difficult from now on. In 1984, Ronald Reagan signed the first presidential directive on computer security, warning of electronic interference by foreign intelligence agencies, terrorist groups, and criminals. The staffers who wrote this document—most of them in the Pentagon and the NSA—knew about this danger because they knew the United States was already hacking into foreign networks, and they inferred that what we could do to them, they could someday do to us.