DESCRIPTION OF EVENTS
"Bithumb is a South Korean cryptocurrency exchange. Founded in 2014, Bithumb Korea is the most influential digital currency exchange in the country, having 8 million registered users, 1M mobile app users and a current cumulative transaction volume has exceeded 1 trillion US dollars."
"Bitcoin Gold was the second fork of Bitcoin when it went live in November 2017 (amidst a few technical issues that occurred pre-launch). Albeit being marketed as a cryptocurrency supporting decentralized mining through an ASIC-resistant mining algorithm, critics of the cryptocurrency called it a “cash grab.” Yet, most bitcoin holders were given free BCG coins relative to their holdings of Bitcoin, so most welcomed the “free money.”"
"In a May 11th blog post, the Bitcoin Gold team made Bitcoin Gold (BTG) holders aware of attempts to attack the Bitcoin Gold network. Exchanges were also asked to guard against the attack since potential attackers were likely to profit by double spending coins in exchange transactions. The blog post was updated on the 24th of May to announce that a dreaded 51% attack occurred on the network between the 16th and the 19th of May 2018. The attack on Bitcoin Gold also involved rented hashpower from cloud mining services."
"Traders of the coin, established in 2017 through a hard fork of the main Bitcoin (BTC) network, have been tracing the attack since last week."
"Scrutiny of unusual activity on the network has revealed the scheme, in which "double spending" attacks have been launched against cryptocurrency exchanges trading the virtual currency."
"A Bitcoin Gold wallet linked to the double spend scheme has received over 388,000 BTG, which is currently worth about $18 million, according to data from CryptoCompare. Most of the coins have now been transferred to various other addresses and only about 13,000 BTG are left in it."
"Bitcoin Gold—already one of the worst performing cryptocurrencies in 2018—faced even more problems after the attack. Bittrex delisted BTG following the BTG team’s refusal to pay compensation of 12,372 BTG. Exchanges including Bittrex, Binance, Bithumb, Bitinka, and Bitfinex lost an estimated $18 million worth of coins due to the double spend attack. Bittrex blamed the Bitcoin Gold team for negligence and demanded compensation in order to keep the cryptocurrency listed."
"In response, the Bitcoin Gold team stated that 51% attacks are a known risk in the ecosystem. They added that the BTG organization was not responsible for the attack since it was not caused by flaws in the Bitcoin Gold blockchain or code. Additionally, the team cited warnings it gave prior to the attack as well as the assistance it gave exchanges for defending themselves."
"The BTG team also claimed that the network upgrade carried out in July 2018 will reduce the likelihood of another attack on the network. Bittrex ended up delisting the coin, along with several others. Bitcoin Gold still survived as the 27th most capitalized coins on CoinMarketCap."
In 2018, a string of Bitcoin Gold 51% attacks targeted multiple platforms including Bithumb. In response to these attacks, the block confirmation times were increased.
HOW COULD THIS HAVE BEEN PREVENTED?
51% attacks can be prevented through a mix of increased block confirmation times and setting checkpoints to prevent large-scale rollbacks. This means the exchange will not credit deposited funds, or nodes will be prevented from accepting the attacking chain.
Five most prolific 51% attacks in crypto: Verge, Ethereum Classic, Bitcoin Gold, Feathercoin, Vertcoin | CryptoSlate (Sep 29)
https://en.bithumb.com/ (Oct 19)
Is The Acquisition Of the Bithub Exchange In Danger? | Tokeneo (Oct 19)
Bithumb: Hackers 'rob crypto-exchange of $32m' - BBC News (Feb 23)
Bitcoin Gold suffers double spend attacks, $17.5 million lost | ZDNet (Nov 9)
Double Spend Attacks on Exchanges - #24 by MentalNomad - Announcements and Site Feedback - The BTG Community Forum (Nov 9)
Bitcoin Gold Hit With 51% and Double Spend Attacks, $18 Million Stolen | Cryptoglobe (Nov 9)
Bithumb - Wikipedia (Nov 10)
Double Spend Attacks on Exchanges - Announcements and Site Feedback - The BTG Community Forum (Apr 29)
Korean Self-regulatory Crypto Industry Body Under Question After 12 Crypto Exchanges Approved | YOUniversityTV (May 8)