US Representative Sean Casten, Democrat of Illinois, along with lawmakers Stephen Lynch, Brad Sherman, Bill Foster and others, sent a letter to the Treasury urging it to investigate illicit financing through cryptocurrency mixing services, particularly Tornado Cash. "Despite the sanctions, Tornado Cash remains online and continues to function as a decentralized smart contract," the lawmakers said in the letter. The US Treasury's Office of Foreign Assets Control (OFAC) designated Tornado Cash as a sanctioned entity in 2022. The group of lawmakers asked the Treasury Department to answer questions about cryptocurrency mixers by Dec. 2, including estimates of Tornado Cash activity since August 2022, whether sanctions have led to an increase in suspicious activity reports, and whether additional sanctions are being considered.