The U.S. and U.K. are investigating several cryptocurrency transactions valued at more than $20 billion that passed through a Russian-based virtual exchange, Bloomberg reported on March 28. The transactions were reportedly made through the Russian-based exchange group Garantex using the dollar-pegged cryptocurrency Tether. The U.S. and U.K. have sanctioned transfers through Garantex on suspicion of enabling financial crimes and illicit transfers to Russia. Western countries have launched several rounds of sanctions against Russia and individuals associated with Vladimir Putin since the beginni…