https://motherboard.vice.com/en_us/article/ne3pwk/an-alleged-hacker-stole-dollar30-million-in-cryptocurrency

Cryptocurrency startup Tether announced late on Monday night that an “external attacker” stole more than $30 million USD worth of digital money from the company.

Tether issues digital tokens backed by its own reserves of fiat money (one USDT token is equal to one dollar USD, for example) over a protocol called Omni that runs on the Bitcoin blockchain. The company is a major player in the cryptocurrency space, and several large exchanges have integrated Tether as a method of payment.