"The idea came from the shocking images from the Middle East and the way cultural history is just being destroyed by Islamic State," said one of the team with a background in the British special forces.
"It just flies in the face of everything that's decent. Anyone can see that destroying the world's cultural heritage in the name of religion or faith is just wrong."
The small anonymous team go by the bland name of the Committee for Shared Culture, which gives little hint as to the nature of their task.
Their mission to save the imperilled archaeological heritage of the Middle East has also led them to be nicknamed the digital Monuments Men, after the team of academics portrayed in the 2014 George Clooney film, who tried to save art treasures from the Nazis.
"We have got very good over the last ten years at finding people," the source said.
"Everyone leaves a digital trace, on social media, or the web. Now, it's the same for items. Using the same techniques people have been using to map and find terrorists, we can now find items and map networks of smugglers."
Governments are overwhelmed by the scale of the challenge, so the team decided to start on their own. The dozen or so former intelligence workers, academics and linguists are funded by a wealthy private individual with an interest in antiquities, but are also looking for further funding, he said. They choose to remain anonymous for security reasons.
"It came out of a number of conversations with similar-minded individuals and we decided it was something we could do without waiting for somebody else to act."
The spread of extremists such as Isil, also known as Isis or simply Islamic State, has seen not just the wanton destruction of globally important sites such as Nimrud, the ancient Assyrian city south of Mosul, but also an explosion in looting.
The smuggling of antiquities out of the region to black markets in Turkey, Beirut and beyond is now believed to be one of the militants' main sources of income.
France Desmarais, the director of programmes and partnerships at the International Council of Museums, said: "The scale and the rhythm of the looting in Iraq is unprecedented. It's a huge free-for-all."