Bitcoin Gold is one of the many Bitcoin hard forks to have popped up over the years. While the currency has never achieved wild success, it has also not been a complete failure, often ranking in the top 30 digital currencies worldwide. However, the coin is likely going to see a major drop in popularity as it has experienced a massive double-spend attack.
The scenario is perhaps the worst nightmare for any cryptocurrency. An attacker takes control of the blockchain network and uses this to defraud cryptocurrency exchanges, transferring money to hacker-controlled accounts—in this case, around $18.6 million in Bitcoin Gold.
Despite the decentralized nature of the blockchain, an individual or group can take control of the majority of the processing power of a given blockchain and them create fraudulent transactions.
This is a great concern in the cryptocurrency community, especially when computing power for a given currency is concentrated in a specific area. For example, there has been speculation that large computing centers set up in a specific country could provide 51 percent or more of the computing power for a given cryptocurrency, and then the government of that country would effectively have control over the currency.
This is unlikely for larger currencies. For example, Bitcoin and Ethereum likely have nothing to fear. But smaller coins? Such attacks are a real possibility, as Bitcoin Gold has proven.
According to Edward Iskra, Director of Communications for Bitcoin Gold, these attacks have been ongoing for at least a week. Other coins that have recently suffered such an attack recently are Verge, Monacoin, and Electroneum.