In the aftermath of 9/11, New York City law enforcement officials developed a strategy designed to gain intelligence and develop technology to prevent any more attacks. Twenty years and hundreds of millions of dollars later, those same strategies and technological advancements are used to solve crimes.

The NYPD has made significant technological changes since the destruction of the World Trade Center, adding more cameras, installing license plate readers at points of entry as well as in police cars, and giving their officers smart phones that have access to records and information, officials said. These advances, among others, were developed using federal funding.

Since 2017, the NYPD has spent over $300 million each year on intelligence and counterterrorism, according to the city's independent budget office. The tab for 2021 is also expected to be above $300 million, a spokesperson said.

And since 9/11, the NYPD has stopped 51 terror incidents that have either emanated from New York City or where the city was the target, according to John Miller, deputy commissioner for intelligence and counter terrorism. And 25 of those incidents have happened within the last five years, according to Miller.

The department's anti-terror tools also are being used to solve more run-of-the-mill crimes.

"The systems that were built with Homeland Security funding in the years after 9/11 are for protecting New York City from the threat of terrorism," Miller said. "We would be remiss, and the federal government fully agrees with this, if we did not use those same tools to fight crime. Our job is to protect life and property and dual use for these tools is a legal and accepted practice."

Suspects tracked from 'beginning to the end'

NYPD officials were notified of a heist at a luxury retail store in Manhattan on Aug. 20 where $20,000 worth of handbags were stolen. Five men hopped into a stolen Range Rover and fled with the high priced handbags. Investigators used their plate readers to find them hours later on their way to New Jersey using the Lincoln Tunnel.

The NYPD also used license plate readers to catch Grafton Thomas after federal prosecutors said he entered into a rabbi's home in Monsey and attacked five people with an 18-inch machete. Thomas was arrested an hour after the attack when license plate readers identified his vehicle crossing the George Washington Bridge into New York City, authorities said at the time.

Former NYPD Chief of Department Terence Monahan says the biggest tool investigators use now is cameras. The prevalence of those cameras allow investigators to follow someone in the moments before they commit a crime and after. Those cameras in combination with license plate readers are what make the difference in solving crimes, Monahan said.

"We can track a person from the beginning to the end," Monahan said. "If he's wearing a mask when he does the crime we're gonna catch him three hours later without that mask, because we've tracked them all along. We've tracked cars for miles and miles after an incident and see him get out of the car and then identify who the shooter is."

New York Civil Liberties Union director Chris Dunn questioned the extent to which the NYPD uses technology to fight crime.

"The NYPD's routine use of 9/11-justified technology is a sobering reminder that extraordinary police tactics justified in the name of terrorism inevitably morph into everyday tactics," Dunn said.

Miller defended those tactics.

"Any suggestion that this is some kind of sweeping surveillance program used to 'spy' on everyday New Yorkers, going about their day-to-day business, or to inhibit protest or dissent is an actual fundamental misunderstanding of these tools, what they are for and our own rules and regulations about how they are used," Miller said.

Laura Cooper, executive director of the Major Cities Chiefs Association — a professional organization for executives of police departments — told CNN there's "a delicate balance between weighing privacy with technology."

"You need to have 21st century tools to keep people safe," Cooper said. "I think a lot of departments have worked with a lot of privacy and civil liberties and civil rights groups to strike that balance. Not always perfect by any means. But it's important to have those tools."

Taliban's takeover has consequences

Miller, who presented at the House Committee on Homeland Security in New York City on Thursday, highlighted the Joint Terrorism Task Force, which has over 100 NYPD detectives assigned to it.

Those detectives, tasked with heading off attacks before they happen, have the highest security clearance, can crosscheck FBI databases and are privy to the most sensitive data. They then brief officials in New York on any terror threats that may come.

As of now, the challenge is determining how the recent rise to power of the Taliban correlates to the terror threat.

"What is the loss of control of Afghanistan with at least a U.S. supported government, and some kind of diplomatic and intelligence weapons on the ground mean? The answer is we don't know yet, but the risk is that we're back where we started," Miller said. "The way and the reason a 9/11 could happen and did happen is because al Qaeda was able to have the infrastructure of sanctuary and safety on the ground in Afghanistan unchallenged."

Miller said the picture will become more clear as to whether Afghanistan becomes a safe place to harbor terror.

"Our picture in terms of risk has gotten more complicated and our threat level has picked up a couple of notches and we're going to have to assess that three months out, six months out and a year out from now before we know what that's going to mean," Miller said.

Miller was part of a panel of first responder agencies that took part in a discussion on security after the terror attacks on September 11. Other agencies including the Port Authority Police Department, the FDNY, FEMA and the U.S. Coast Guard also participated.

Miller, who spoke of how the NYPD has advanced their technology to keep pace with the ongoing terror threat and now shares intelligence with other agencies, also spoke about propaganda from terrorist organizations, which has only grown louder since the Taliban's takeover.

"We've seen for the 20th anniversary of 9/11, we see for every anniversary, a spate of 9/11 related propaganda by terrorists entities. In this case, it has been louder, more persistent and better organized. It has been infused with a call to action," Miller said, highlighting the recent suicide bombing in Afghanistan as an example, in addition to the latest edition of Inspire Magazine which he says was released in June.

"Propaganda is a psychological operations tactic, but propaganda has translated to action," Miller said.

U.S. Department of Homeland Security Secretary Alejandro Mayorkas said the threat landscape in the United States has "evolved over the last 20 years," with a greater focus on domestic violent extremists during the last few years, rather than the "foreign terrorist fighter" that had been the focus of threats immediately after 9/11.

"As the threat evolves, it doesn't mean that the prior iteration of that threat has disappeared, but rather we see a rise in prominence of a new threat," Mayorkas said after attending a 9/11 security briefing Friday at NYPD headquarters in Manhattan

Mayorkas also applauded the partnership between local, state and federal partners in working "towards a common goal — the safety and security of the American people."

"As we stand here today, 20 years after the 9/11 attacks, we stand stronger and safer as a country," he said. "And we do so because of the partnership we have built over those many years. We share information, we share and provide equipment, expertise, and talent, and dedication."

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CNN's Peter Nickeas and Laura Ly contributed to this report.