In the first generation of the online revolution, the question would have seemed absurd. In his new book The Perfect Weapon: War, Sabotage and Fear in the Cyber Age, Belfer Center Senior Fellow David Sanger addresses why that question has become less outlandish.

More than 30 high-tech companies, led by Microsoft and Facebook, announced a set of principles on Tuesday that included a declaration that they would not help any government — including that of the United States — mount cyberattacks against “innocent civilians and enterprises from anywhere,” reflecting Silicon Valley’s effort to separate itself from government cyberwarfare.

Although cyber weapons can usually be employed in a far less lethal manner than guided missiles shot from a drone, they have been deployed less frequently and under rules of engagement that are far less clear, at least to the public.

A look at North Korea's latest rounds of missile tests with David Ignatius of the Washington Post, David Sanger of The New York Times, Lionel Barber of the Financial Times, and Nicholas Burns of Harvard's John F. Kennedy School of Government.

"When President-elect Donald J. Trump said on Twitter in early January that a North Korean test of an intercontinental ballistic missile capable of reaching the United States “won't happen!" there were two things he still did not fully appreciate: how close Kim Jong-un, the North’s leader, was to reaching that goal, and how limited any president’s options were to stop him."

American officials have long considered Huawei, the Chinese telecommunications giant, a security threat, blocking it from business deals in the United States for fear that the company would create “back doors” in its equipment that could allow the Chinese military or Beijing-backed hackers to steal corporate and government secrets.

President Obama's administration came to office with the world on fire. Confront and Conceal is the story of how, in his first term, Obama secretly used the most innovative weapons and tools of American power, including our most sophisticated—and still unacknowledged—arsenal of cyberweapons, aimed at Iran's nuclear program.

Confront and Conceal—with an updated epilogue for this paperback edition—provides an unflinching account of these complex years of presidential struggle, in which America's ability to exert control grows ever more elusive.