https://thehill.com/policy/technology/technology/466084-us-authorities-use-bitcoin-trail-to-breakup-large-child-porn :
U.S. authorities followed a bitcoin trail to break up what they described as one of the largest dark web child porn marketplaces.
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Bloomberg reported that investigators were able to track down Son and the location of his "darknet" server by targeting users' bitcoin transactions.
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“Our agency’s ability to analyze the blockchain and de-anonymize Bitcoin transactions allowed for the identification of hundreds of predators around the world,” Don Fort, chief of the IRS Criminal Investigation Division, said, according to Bloomberg. “The scale of this crime is eye-popping and sickening.”