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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