From an office in the Washington suburb of Bethesda, Maryland, a small team scans the web 24 hours a day for jihadi videos often featuring gruesome executions by groups such as Islamic State.
On Tuesday, SITE Intelligence Services grabbed headlines when it found and alerted its subscribers to footage of the beheading of Steven Sotloff, the second American journalist to be put to death by IS in two weeks.
Founded by Iraqi-American Rita Katz, SITE has built up more than a decade of experience tracking extremist groups online for clients including government agencies of the United States and other governments, private firms and media outlets.
Katz would not disclose the number of staff but said it was a small and dedicated team.
By monitoring file-sharing sites, Islamist forums and other obscure and often password-protected areas of the Internet, the firm says it has built up a sophisticated picture of how Islamic State and similar groups operate online.
"Our ability to find jihadist materials so quickly doesn't come from luck," Katz said. "Tracking them is a science."
With intelligence agencies stretched and ever more information available online, current and former Western officials say governments are turning increasingly to private companies for such monitoring.
While militant groups have long used videos and the Internet to share their message and threats, IS has embraced social media like no jihadi group before it. It has multiple supporters posting messages and content on Twitter, Google Inc's YouTube and elsewhere.
Monitoring such messages, experts say, can provide invaluable formation about organisational structures.
NOT FOR THE FAINTHEARTED
"It's grim but it does shed continuing light on the Islamic State and its handling of social media," John Bassett, a former senior official at British signals intelligence agency GCHQ, said after the beheading of U.S. reporter James Foley last month.
"They are more social media savvy than Osama bin Laden. They are switched on enough to use a Brit to narrate a beheading video," he said. Video of the two hostages killings by Islamic State featured a masked militant speaking with a British accent.
Katz said the most useful material remained on more hidden jihadi sites. That was where groups such as IS posted the original videos and statements for other supporters to circulate more widely through mainstream social media like Twitter.
"There is a very strict and clear process by which jihadi groups release their propaganda," she said. "This process makes it easy for the followers to differentiate between official and unofficial releases."
In the case of the Sotloff video, Katz said Islamic State had intended to further edit the footage and simultaneously release versions in multiple languages, including French, Russian and German, in an apparent attempt to boost recruitment.
Comments posted on jihadi forums indicated that SITE's discovery of the video and the early release of its version had been an embarrassment to some members of the group, she said.
The emotional toll of watching such scenes, experts say, can be high.
"SITE employees fully understand the ghastly scenes such as beheadings are the nature of the work in the counterterrorism field, just as surgeons recognise they will see blood on the operating table," Katz said.