Tether, the $84 billion so-called stablecoin bridging the worlds of cryptocurrencies and the dollar, is increasingly showing up in investigations tied to money laundering, terror financing and sanctions evasion.

Tether is now the world’s most heavily traded cryptocurrency by volume. The stablecoin, also known as USDT, maintains a 1:1 exchange ratio with the dollar. Traders use it to stash their cash, easily invest in other cryptocurrencies or swap it into traditional currencies such as the dollar.