Reddit user SpeedflyChris published the results of his cryptoramination from the blockchain. He has found that the Tether’s hack is very similar to Bitstamp’s hack in 2015 year. Then was lost 19000 BT.
The user considers that the Tether vulnerability appears’ source is connected with the wallet used to steal from Bitstamp. This wallet was used to make 2 transactions with 0.01 BTC for each to the address.
SpeedflyChris wrote that this wallet made two transactions, the first is fairly innocuous and illustrated it by link.
Then it removed $30,950,010 USDT from the Tether and sent it to final bitcoin address. This transactions was structured like an additional security layer and this allowed hackers to get tokens without any problem.
Also SpeedflyChris thinks that with this wallet was stolen 12000 BTC from Huobi in 2015 year. Then was used exactly the same scheme with microtransactions which was used with Bitstamp and Tether.