This post has been updated to add subsequent comment from Babel Street.

In a small office in Ashburn, Va., ensconced among the government contractors that make up the Dulles Technology Corridor, a start-up called Babel Street is bringing government-style surveillance to an entirely new market.

The company's Web crawlers, offered under a subscription called Babel X, trawl some 40 online sources, scooping up data from popular sites such as Instagram and a Korean social media platform as well as inside "dark Web" forums where cybercriminals lurk.

Police departments investigating a crime might use the service to scan posts linked to a certainneighborhood over a specified period of time. Stadium managers use it to hunt for security threats based on electronic chatter.

The Department of Homeland Security, county governments, law enforcement agencies and the FBI use it to keep tabs on dangerous individuals, even when they are communicating in one of more than 200 languages, including emoji.

The firm, staffed by former government intelligence veterans, is part of an insular but thriving cottage industry of data aggregators that operate outside of military and intelligence agencies. The 100-person company said it is profitable, something that is rare for a tech start-up in its third year. (It declined, though, to release financial details.) It recently took on $2.25 million from investors, bringing its total capital raised from investors to just over $5 million.

A U.S. subsidiary of the European software giant SAP is its largest institutional investor.

Businesses like Babel Street have to tread an ethical line to avoid igniting privacy concerns, even though the data they access is generally publicly available on the Internet. Groups such as the American Civil Liberties Union (ACLU) regard the industry's growth as a worrying proliferation of online surveillance.

"These products can provide a very detailed picture of a person's private life," said Matt Cagle, an ACLU lawyer who studies the issue.

Last year, Chicago-based social media aggregator Geofeedia was thrust into the national spotlight when the ACLU published a report alleging it had helped police departments track racially charged protests in Baltimore and Ferguson, Mo.

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The report prompted Twitter, Facebook and Instagram to cut ties with Geofeedia, eliminating important data sources. The company laid off half of its employees soon afterward amid a broader restructuring.

Perhaps as a result, Babel Street does not access individuals' people's Facebook profiles, though the company's executives say they have "a close relationship with Facebook."

Babel Street's executives say they have avoided controversy by closely adhering to privacy standards and limiting law enforcement officers' access to the social media information they collect.

"If someone has arrest powers, they get less access to the data than other customers," said Jeff Chapman, a former Navy intelligence officer who founded Babel Street in 2014.

The Pentagon was Babel Street's first customer. Agencies focused on counterterrorism would use the company's technology to monitor terrorists' online chatter to predict attacks. Police departments and the FBI soon started signing up for the service, public contract documents reviewed by The Washington Post show.

The Department of Homeland Security pays for the product through "fusion centers" that gather and pass data to state and local first-responders, showing them the electronic footprint of an emergency event in real time.

"They've got the ability to go in and look at the entire spectrum of social media platforms," said Lee Smithson, executive director of the Mississippi Emergency Management Agency, which coordinates the state's disaster response activities.

"They'll look for keywords like 'rescue' or 'dire situation' . . . that kind of thing. And they'll pass those messages to us," he said.

During the past few years, Babel Street has been doing more and more work for private industry.

Chapman says word spread about the business when government chief security officers left their posts for lucrative private-sector gigs, bringing Babel Street business in the process.

Guiding the company as an investor and board member is Arthur Money, a former chief information officer at the Pentagon who later became involved in the business side of government intelligence work.

Money is the former chairman of the FBI's Science and Technology Advisory Board and is a board member for privately held intelligence contractor Keyw, a Maryland-based cybersecurity company.

Money also has ties to numerous defense and intelligence businesses including Kestrel Enterprises, an intelligence analytics company owned by defense giant Boeing.

Today about half of Babel Street's users hail from the private sector, Chapman says. The shift has been good for business: Chapman says the company has a few thousand users, some of them paying more than $20,000 a year for a subscription.

As the Internet has evolved, Babel Street's intelligence work has evolved with it. Emoji have been a challenge for Chapman's team of technologists lately, for example.

"We are seeing emoji increasingly used to get around text analysis," Chapman said. "Guys that want to be nefarious in their activities will use things like emoji to communicate with each other."

Brand management has become an important line of business, as corporations face the increasingly difficult challenge of tracking their digital reputations. Some companies pay Babel Street to find out whether their intellectual property is being used without permission.

The company is even getting involved in hurricane response. The firm has trained its Web crawlers to look for people stranded in Houston's floodwaters or waiting out Hurricane Irma in Florida. They are tracking online scammers that might try to profit from the disaster.

Chapman says Babel Street's brand of public metadata collection will one day be just as important to first responders as 9-1-1 phone lines.

"There are billions of smartphones on the planet," Chapman says. "All you have to do is listen to them."

A spokesperson representing Babel Street contacted the Washington Post following the publication of this story to say the company does not literally listen to private phone calls. The company gathers information from public social media postings and websites.