Internet Giants Erect Barriers to Spy Agencies

MOUNTAIN VIEW, Calif. — Just down the road from Google’s main campus here, engineers for the company are accelerating what has become the newest arms race in modern technology: They are making it far more difficult — and far more expensive — for the National Security Agency and the intelligence arms of other governments around the world to pierce their systems.

As fast as it can, Google is sealing up cracks in its systems that Edward J. Snowden revealed the N.S.A. had brilliantly exploited. It is encrypting more data as it moves among its servers and helping customers encode their own emails. Facebook, Microsoft and Yahoo are taking similar steps.

After years of cooperating with the government, the immediate goal now is to thwart Washington — as well as Beijing and Moscow. The strategy is also intended to preserve business overseas in places like Brazil and Germany that have threatened to entrust data only to local providers.

Google, for example, is laying its own fiber optic cable under the world’s oceans, a project that began as an effort to cut costs and extend its influence, but now has an added purpose: to assure that the company will have more control over the movement of its customer data.

A year after Mr. Snowden’s revelations, the era of quiet cooperation is over. Telecommunications companies say they are denying requests to volunteer data not covered by existing law. A.T.&T., Verizon and others say that compared with a year ago, they are far more reluctant to cooperate with the United States government in “gray areas” where there is no explicit requirement for a legal warrant