On 8 August 2022, the US Treasury's Office of Foreign Assets Control (OFAC) sanctioned Tornado Cash,  an online service that has served as a mixer for the Ether cryptocurrency since 2019. Cryptocurrency mixers are online places where users could obfuscate the origin of cryptocurrency. Mixers use decentralised exchanges and peer-to-peer trading to create a massive number of transactions in a short period of time -mixing tinted coins with the rest of the online supply. Mixers do not collect any user data related to people behind the cryptocurrency funds, therefore violating US federal and global AML/CFT regulations.

The Treasury cited national security issues as one of the reasons for such action. The FBI and OFAC are arguing that Tornado Cash facilitated a money laundry operation for the ransomware group Lazarus attributed to the DPRK. OFAC is calming that cryptocurrency mixer was mostly used for illicit funds and has issued a list of Ether wallet addresses that are sanctioned in this case. It is not common practice for OFAC to sanction online services as their main targets are individuals.
OFAC has called for the cryptocurrency industry to address the challenges that anonymisation features may pose to AML/CFT obligations.

Tornado Cash is a decentralised entity that runs on open-source code.