The blacklisting of marks the first time the Treasury has placed a cryptocurrency mixer on its sanctions list. The U.S. Treasury’s Office of Foreign Assets Control, which implements and enforces the sanctions, said operates on the bitcoin blockchain.

Treasury: has helped transmit more than $500 million worth of bitcoin since its creation in 2017. Treasury: Virtual currency mixers that assist illicit transactions pose a threat to U.S. national security interests. The Treasury also alleged helped launder money for several Russian-linked ransomware groups.

The Treasury said was involved in laundering more than $20.5 million of proceeds from the Lazarus Group’s nearly $620 million cryptocurrency heist. The Lazarus Group, which the U.S. sanctioned in 2019 alleging it was an agency of the North Korean government, was the largest virtual currency heist to date.