“The core of the operation was an online money-laundering business seized by agents from Homeland Security Investigations and operated as a sting for over a year. By offering cash for bitcoin, HSI agents were able to identify specific drug dealers, ultimately tracing more than $20 million in drug-linked cryptocurrency transactions.”
Read more: https://www.theverge.com/2018/6/27/17509444/dark-web-drug-market-money-laundering-hsi-dark-gold