The killer storm that pummeled the East Monday and left the nation's largest city with a crippled transit system, widespread power outages and severe flooding has resurfaced the debate about how best to protect a city like New York against rising storm surges.

"Hurricane Sandy is a wake-up call to all of us in this city and on Long Island," Malcolm Bowman, professor of physical oceanography at State University of New York at Stony Brook, told NBC's Richard Engel, who surveyed the damage from a police helicopter Thursday. "That means designing and building storm surge barriers like many cities in Europe already have."

Bowman points to storm surge barrier projects in St. Petersburg, Russia, and in the Netherlands as models. In the Netherlands, a country where a considerable part of the population lives below sea level, such barriers help control flooding in some of the most densely populated areas.

"If we had such barriers in place during Hurricane Sandy there would have been no damage at all," Bowman said.

Before the storm, Mayor Michael Bloomberg's administration had said it was working to analyze natural risks and the effectiveness of various coast-protection techniques, including storm-surge barriers. But officials had noted that barriers were only one of many ideas, and they have often emphasized more modest, immediate steps the city has taken, such as installing floodgates at sewage plants and raising the ground level while redeveloping a low-lying area in Queens.

"It's a series of small interventions that cumulatively, over time, will take us to a more natural system" to deal with climate change and rising sea levels, Carter H. Strickland, the city's environmental commissioner, told The New York Times this summer.

Sandy sent a record 14-foot storm surge into New York Harbor, flooding subway tunnels and airports. It forced the closure of the stock market for two days, the first time that's happened for weather-related reasons since 1888. There's no estimate yet for the cost of the devastation in New York City, but forecasting firm IHS Global Insight put the cost of the damage along the coast at $20 billion, plus $10 billion to $30 billion in lost business.

Graeme Forsyth, an engineer for CH2M Hill in Glasgow, Scotland told The Associated Press that his firm's early-stage proposal for New York is a levee-like barrier that would stretch five miles from the Rockaway peninsula in Queens on Long Island to the Sandy Hook promontory in New Jersey. The barrier would stop a surge of 30 feet, twice the height from Sandy. Gaps would allow ships, river water and tides through, but movable gates could close off all of New York Bay from the Atlantic when necessary. The barrier would protect most of the city, with the exception of Rockaway itself. It would also shield parts of New Jersey.

An animation, produced by the Dutch company Arcadis, shows how a sea gate could protect New York Harbor when a storm surge is imminent. The gates would close and block the water from entering the harbor until the danger has passed.

"Some people may say that storm barriers are an extreme solution," Bowman told NBC News. "I just would say it's bold, it's imaginative, it's permanent in the sense that it could protect the city for another 150 years. The Europeans have done it, why can't we?"

Some scientists, however, say there needs to be a holistic approach and that barriers are only one part of the solution.

Cynthia Rosenzweig, a senior research scientist at the Goddard Institute for Space Studies at Columbia University, told NBC News that as the region rebuilds, developers must take into account rising sea levels.

"The better way is for New Yorkers to be smart from engineered solutions like tidal barriers, fixing the subways where they're vulnerable, fixing our sea walls, remaking our wetlands so that we can, across our whole region and for all our 21-and-a-half million people, protect against the next Hurricane Sandy," Rosenzweig said, adding that even the Dutch now admit they can't protect everyone with barriers.

In the wake of Sandy, Bloomberg, too, appeared skeptical.

"I don’t know that I think there’s any practical ways to build barriers in the oceans, when you have an enormous harbor like we do," he said in a press conference.

But for Bowman, the time to act is now.

"It's a question of national security. It's a question of survival. It's a question of the future population being able to live there so it's taken very, very seriously," he said.

The Associated Press contributed to this report.

Rock Center

It was a crime of staggering sophistication by computer hackers who figured out a new way to get rich. 

In a case that became known as Trident Breach, the hackers stole $70 million from the payroll accounts of some 400 American companies and organizations – all from the safety of their homes in Eastern Europe.

“I think it’s the perfect definition of organized crime,” said FBI Executive Assistant Director Shawn Henry.  “It’s very well organized.  It’s very well-structured.  It requires many people operating in unison, in a collaborative way.”

At the beginning of 2008, the group of hackers compromised hundreds of thousands of Americans computers using a malicious computer “Trojan” bug called ZeuS. When computer users clicked on certain attachments and e-mail links, ZeuS infected their computers.

ZeuS is designed to zero in on users’ bank information. For example, when a user visits a bank website, ZeuS knows; and since it is a key logger program, it records the user's keystrokes as he or she enters usernames and passwords. It then sends that information by instant text message to waiting hackers, who then have access to the compromised accounts. 

Henry is one of the country’s top cybercrime fighters. He says Americans are increasingly prone to “virtual gangs” prying on people’s personal data stored on their computers.

“We have organized groups that have developed internationally where groups of people have come together, each with a very specific capability and skill, who have never met each other in the physical world, but they meet online in a collaborative way,” he said. 

Henry says that the security breaches have the potential to be more than just criminal acts. They could pose a national security risk.

“There are foreign intelligence services that are aggressively pursuing American technology.  They’re aggressively pursuing American strategy.  They’re looking at the American military, the American consumer, the American corporations, research and development organizations, laboratories, educational facilities,” Henry said.  “The amount and value of data that is on the network is at an unprecedented level.  Our adversaries know that that data is there.  It’s information and information is valuable."

Money Mules Help Hackers Get $70 Million

In the Trident Breach case, the hackers were able to get their hands on the cash by turning people into money mules.  

Beginning in late 2008, they created some 3000 money mules, many of them unwitting Americans, by luring them into work-at-home jobs requiring "employees" to open bank accounts. 

“The first money mule activity we started seeing was people who would receive an email saying, ‘You can get a work-at-home job’ and the work-at-home job would be something like transaction manager for an international company,” said Prof. Gary Warner of the University of Alabama at Birmingham, who teaches a program that combines computer forensics and justice studies. 

Warner is also a member of the little-known FBI-affiliated group called InfraGard, comprising some 50,000 members across the United States who keep an eagle eye on U.S . critical infrastructure: power plants, water supply, security and financial services…and the internet. Warner said the hackers transferred cash from business payroll-type "ACH" (Automated Clearing House) accounts to the mule accounts and the mules sent the cash by Western Union or MoneyGram to Eastern Europe, taking eight or 10 percent commission.

Warner said that when the banks started to get wise to the hackers’ work-at-home schemes, and set up roadblocks, the hackers then recruited dozens of students, mainly from southern Russia, to be a new breed of money mule. 

“It’s still a little gray whether the students who were recruited knew that they were being recruited for crime,” Warner said.

The hackers obtained fake passports for the students, U.S. J1 work/study visas, and packed their new mules off to the United States. The students opened multiple bank accounts, mainly in the New York area, where they received stolen cash. Then, just as the mules before them had, they wired the cash back to their bosses. 

University Professor Helps FBI Crack Cybercrime Case

So stealthy was their ZeuS operation, neither the hackers nor the mules had counted on getting caught. But, using complex data mining techniques, Prof. Warner established links between ZeuS-infected computers and traced the origins of the mass infection to Ukraine; and many of the hackers and their mules were caught.

But 18 mules remained at large in the United States. And after the FBI published a wanted poster of the students, Warner’s students began using what they’d learned in class to track the criminals.

“So the students used the techniques we had taught them during investigating online crime [class] and began crawling Facebook pages and VKontakte, which is a Russian version similar to Facebook and were able to quickly identify profile pages of almost all of them, at-large mules,” Warner said.

Warner’s students discovered one of the students-turned-mules had brazenly posted pictures of herself with a wad of hundred-dollar bills. Another had posted a picture of himself dressed in an “I ❤ New York” top, arms aloft, celebrating in a bar with his friends – some of whom turned out to be other money mules. And another was pictured standing next to the new car he has presumably just bought.  

Though all the mules – except one – were arrested, that does not necessarily mean the end of the money mules, says Gary Warner.

“ZeuS infections are rampant still today.  There are probably millions of computers in the United States that have active Zeus on their machines right now,” Warner said.

Editor’s Note: Click here to watch Richard Engel’s full report, 'Easy Money,' from NBC's Rock Center with Brian Williams.