BITTREX

DESCRIPTION OF EVENTS

“Bitcoin Gold was hijacked with rented computing power. After hackers took control of more than 51 percent of the overall hash power, more than 388,000 BTG (approx. $18 million at the time) was stolen from cryptocurrency exchanges like Bittrex. Hackers were able to use “double-spending,” a method of repeatedly tricking an exchange into transferring more coins than it should.”

It isn’t known the exact amount taken from Bittrex through the 51% double spend attack, however they demanded $255k from Bitcoin Gold developers or the coin would be removed. Bitcoin Gold is now notorious for the ease with which double-spend attacks can occur. The solution is a simple and reasonable delay on larger withdrawals, which would normally be in cold storage.

Q3 2018 Cryptocurrency Anti-Money Laundering Report - CipherTrace (Feb 15)
Double Spend Attacks on Exchanges - Announcements and Site Feedback - The BTG Community Forum (Apr 29)
Bitcoin Gold suffers double spend attacks, $17.5 million lost | ZDNet (Nov 9)

More case studies

Taylor
Ethereum Hack

Binance Bitcoin
Gold 51% Attack