Expanded surveillance by the U.S. government was cast as a price of war in the aftermath of the Sept. 11, 2001, terrorist attacks. Yet nearly a dozen years later, the war on terrorism is showing signs of ebbing while the surveillance systems crafted to fight it continue unabated.

If anything, they are becoming more powerful.

That is because the United States went to a war footing at a time of profound technological change that fueled an explosion of personal data. Governments and businesses worldwide have developed the ability to mine, sort and analyze this information as never before — and they show little inclination to relinquish that power.