TOM DRAKE ARRIVED at work on his first day as a full-time employee of the National Security Agency before sunrise on a cool, clear morning: September 11, 2001. As he shadowed the NSA’s director of signals intelligence in a briefing about a new $4 billion plan, codenamed Trailblazer, that would better apply the agency’s spying to the Internet, an aide opened a door and interrupted with news: A plane had hit the north tower of the World Trade Center. Minutes later, the aide returned. The south tower had been hit, too. Drake, a thin man with severe, deep-set eyes, stood up and said the words everyone in the room had been thinking: “America is under attack.” The agency’s modernization plan was already too late.

The director, Drake remembers, was whisked onto an express elevator to a crisis war room. Drake and thousands of other employees were sent home, as rumors swirled that Fort Meade might be the next target. The exodus caused a traffic jam. “We just sat in traffic, stunned.”

In the weeks and months that followed, the NSA indeed transformed, along with the rest of America.  “It was clear that it was going to be a different world…that this was not going to be a normal crisis, but a years-long crisis,” Drake says. Today you can see just how much that moment reshaped America, in how you travel, the buildings you live in, the things you fear, and the privacy you expect. That’s the technological legacy of 9/11—an almost incalculable change to the visible and invisible infrastructure of everyday life.

The Surveillance State

American surveillance was reborn on September 11, and no single government agency embodies that change better than the National Security Agency. After the Cold War, the NSA had been reduced to a kind of backwater within the Pentagon, says James Bamford, the author of a trilogy of books on the agency. By the mid-1990s, it began to position itself as the go-to agency for preventing terrorism. But to do so required a fundamental shift in mission, from targeted eavesdropping on government satellite channels to eavesdropping on the far more diverse forms of communication used by terrorists, like cell phones and the nascent Internet. So the agency needed money.

After 9/11, it got it—coupled with the legal authority and the political mandate to take on that immense spying task. The Patriot Act, rushed through Congress within a month, allowed the NSA to suck up data from telecom and tech firms like never before (leading to the warrantless wiretapping scandal revealed by the New York Times in 2005). A provision of the law—Section 215—allowed the agency to continue collecting the metadata of every American phone call for well over a decade, until Edward Snowden’s leaks exposed the program in 2013 and led to its suspension.

With the benefit of hindsight, it isn’t hard to see that the law, and the NSA’s mandates, would lead to enormous—and now very familiar—problems.

After only a year working full-time in-house at the NSA, Drake began whistleblowing, fighting what he has described as corruption in the NSA’s ballooning, contractor-laden Trailblazer program budget and the agency’s jettisoning of privacy protections. Trailblazer was the beginning of the digital tracking of communication that has been so controversial in the years since Snowden’s leaks, and which involve every aspect of US intelligence and law enforcement, from the CIA to local police precincts.

Drake was prosecuted for mishandling NSA secrets—he served as a source for the Baltimore Sun but maintains he never actually leaked any classified document—an indictment that ended with a misdemeanor conviction but cost him his intelligence career. “Trailblazer was an utter failure. Six years, umpteen billions, no one knows the full number,” he says. And the mindset that led to that waste and privacy invasion continues, Drake argues. “History is pre-9/11 and post-9/11,” he says. “National security has become our state religion.”

Changes You Can See

Nowhere is this religion more apparent than at the airport. Al-Qaeda jihadists turned planes into missiles against US targets, leading to the creation of the Transportation Security Administration. Airlines handed over screening duties at airports to a dedicated government workforce, and airport security changed forever. Today the TSA is a $7.5 billion bureaucratic behemoth that employs 46,000 screeners.

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The political scientist Mika Aaltola describes the post-9/11 airport as an “aviopolis,” where touchstones like putting laptops into plastic bins, a pat down, and a blaring reminder not to carry packages for strangers “drive home the fact that the survival is at stake in the post-September 11th world.” He describes the aviopolis as “tense, nervous and, occasionally, highly dramatic,” a particularly apt characterization in the wake of scares in some of America’s busiest airports.

It’s not just airports. Following the attacks in 2001, federal, local, and state law enforcement agencies started protecting special events. Over time, that meant greater police presence at everything from New York Giants football games to Taylor Swift concerts. While lots of us remember being able to walk into a stadium with the scantest of bag checks, we’re now accustomed to a procedure not all that different from airport security lines: metal detectors, wands, and even pat-downs. “I think it has taken most of 15 years for the American people to get used to these ideas, but it seems to me now that there’s very little pushback,”says William Banks, the director of the Institute for National Security and Counterterrorism at Syracuse University. “I think we’ve just come to accept these differences in our way of life.”

Once a privacy debate lightening rod, even body scanners aren’t so controversial anymore to most Americans, according to a study by researchers at James Madison University.  “In general I think people who fly understand that they want to be safe, and in their own minds think, ‘What may I give up to maintain my safety?’” says  Thomas Dillon, an information security and privacy specialist.

Children born in the years after September 11, 2001 will never experience meeting relatives at the gate. The scene inLove, Actually, where families gather in the terminal to shower Hugh Grant and the rest of the characters with hugs and flowers will seem implausible at best. If you remember when flying was a more casual affair, that kind of movie scene appears now as a throwback to a more naive time.

Banks sees a future where attendance at concerts and sporting events is monitored ever more closely but less obviously, with drones, stingrays, and  biometric systems paired with watchlist databases (in many cases—like theSuper Bowl—this is already happening). ”It won’t be noticed as much by many people,” Banks says, “but they may in some ways be more pervasive than the physical security.” After all, physical security screeners see what’s in your bag and your pockets; aerial and digital surveillance sees behavior, and potentially everything else.

Invisible Redesign

Airports and sports stadiums make intense security measures obvious, but the world around us has changed in less overt ways as well. Since 2001, data centers now get built in varied locations, spread across the country, so that Internet and cellular service won’t collapse everywhere if a crisis strikes one. Today all new high-rises in the US are built around massive concrete cores, mandated by building codes requiring  greater structural integrity. You can witness this design in action in San Francisco’s massive Salesforce Tower, which will be the tallest building in the city. San Franciscans have been watching it go up since 2013, and can clearly see the concrete cylinder that forms its spine. In addition to these cores, new codes mandate wider stairwells, to help people evacuate more quickly. Such utilitarian changes require sturdier construction, but these fortresses are built to look airy and light. They are bunkers hiding in plain sight, their delicate glass exteriors reflecting clouds that hide backbones of steel and concrete.

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The most famous example is at WIRED’s New York offices, the headquarters of Conde Nast in One World Trade Center. The building’s 70-foot-tall concrete base, meant to withstand bomb blasts, is covered in a two-layer screen of stainless steel wire panels with LED lights that give visitors the feeling they are looking at a prism. The lobby, like that of many new office buildings, eschews intimidating security stations and a bevy of security guards in favor of hidden unobtrusive cameras and other automated tracking mechanisms. In other words, security at One World Trade is embedded in every square foot.

New US embassies are designed and constructed without heavy walls or fences. At the new embassy in Beijing, architects replaced those eyesores with a Chinese garden with courtyards, pockets of green space, and a giant reflecting pool. This oasis acts as a vast perimeter wall that protects the glass-walled building from the reach of potential attackers. At the new US embassy in London, architects built a glassy box structure with tiered windows that appear open, encircled by a park and a large pond. The building’s base consists of exposed concrete columns that protect and ground the glass section above. What looks like a post-post-modern pairing of brutalism and contemporary design is in fact a clever way to prioritize security without anyone noticing.

Invisible security, disguised as elegant open space, is a gentler form of what architects refer to defensible space. As more public spaces become potential targets, the need for defensible space grows. And out of this necessity, designers have innovated, figuring out new ways to create public spaces that appear open and unoppressive while subtly encouraging safety.

A Decentralized World

Of course the security goals for new design are ever changing, because terrorism itself has changed. After the US decimated the highest ranks of Al-Qaeda leadership, culminating in Osama Bin Laden’s assassination in 2011, terror networks accelerated their shift toward more decentralized structures. With the help of an ever-more connected world, terrorists can more easily become radicalized from anywhere. ISIS is far less hierarchical than Al-Qaeda was, so the US and our allies will find it nearly impossible to cut off its head.

The increasing decentralization of terrorist organizations has also altered the kinds of attacks they will carry out. Unlike al-Qaeda, today’s jihadist groups have not invested millions of dollars and years of planning into spectacular attacks on American soil—perhaps in part because they’re well-aware of how our domestic security has improved. Our government agencies, despite the years of criticisms, are better coordinated, our airports are safer, our buildings stronger. So today’s terrorists have learned the power of unpredictability, going after “soft targets” like office parties, in the case of the San Bernardino shooting, or night clubs.

The people who carry out those attacks have only the vaguest of ties to the terrorist organizations they claim to support. They are instead individuals who have latched onto the jihadist “brand,” often through social media—a phenomenon that didn’t exist in 2001. And when they do strike, those same technologies amplify their actions—smartphones equipped with high-resolution cameras or apps that can deliver eyewitness accounts of carnage. The companies that have given us those technologies are, for the most part, trying to deal with the changing landscape of risk, to minimize harm and maximize convenience. And in the process they help both the radicalized and their victims, by giving each side more opportunities to connect.

For instance, in the hours after 9/11, when cellphones were not working in much of Manhattan and family members waited in horror to find out if their loved ones were alive, people took to posting paper flyers seeking information. Now Facebook’s billion users can  let their friends and family know they are safe during a disaster by clicking a “Safety Check-In” button. Technology companies in the US are making plans to use drones and high-altitude balloons to deliver communication to people during crises. Microsoft is even developing a submarine that would provide cellular and data connections to an entire coastal city. Such a submarine might one day soon be able to park in New York harbor and keep first responders and citizens connected during a terrorist attack or natural disaster.

So many of us who watched the towers fall knew immediately that life in the United States had changed forever. Now, as WIRED writers look out the window of the new World Trade Center, watching New Yorkers zip past the 9/11 Memorial riding Bluetooth-connected hoverboards, surveilled by cameras embedded in the new “Oculus,” we can see just how extensive those changes really were. And sometimes we can’t. But they’re there.