U.S. and U.K. authorities are investigating cryptocurrency transactions linked to Russia, with transactions totaling over $20 billion passing through the Russian crypto exchange Garantex. This move is part of efforts to prevent sanctions evasion supporting Russia’s war in Ukraine.

The transactions in question were conducted using the Tether (USDT) stablecoin through the Moscow-based cryptocurrency exchange. Garantex faced sanctions from the U.S. and U.K. for allegedly facilitating financial crimes and illegal transactions in Russia.

President Joe Biden’s administration has been actively targeting cryptocurrency exchanges like Garantex since the onset of the war. The $20 billion in transactions under review could be one of the most significant breaches of sanctions against Russia.

The Office of Foreign Assets Control (OFAC) sanctioned Garantex in April 2022, alongside the darknet marketplace Hydra, labeling Russia as a hub for cybercriminals. OFAC criticized Garantex for disregarding anti-money laundering and counter-terrorism financing obligations.

In response to the conflict in Ukraine, western nations have implemented strict sanctions against Russia, prompting regulators to closely monitor the use of cryptocurrencies to evade sanctions. The U.S. Treasury Department recently added 13 companies and two individuals involved in cryptocurrency trading to its sanctions list.

Brian Nelson, the U.S. Treasury Undersecretary for Counterterrorism and Financial Intelligence, highlighted Russia’s shift towards alternative payment methods to bypass U.S. sanctions and fund the war in Ukraine. This underscores the growing concern surrounding the use of cryptocurrencies in sanctions evasion.