Summary # On March 23, 2022, Ronin Network, a blockchain that powers the popular game Axie Infinity, suffered a 51% attack. This allows the attacker to control the network via compromising validators private keys and perform malicious actions, such as double-spending transactions or preventing new blocks from being mined. The attack resulted in the theft of $625 million worth of Ethereum and USDC. The hackers were able to reorganize over 100 blocks, which allowed them to double-spend large amount of assets.
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Summary # Ethereum Classic, a well-known cryptocurrency, experienced a series of three 51% attacks in August 2020. The attackers reorganized over 14,000 blocks and managed to double-spend ETC coins.
Attackers # The identity of the attackers behind the Ethereum Classic 51% attack remains unknown.
Losses # During the Ethereum Classic 51% attack, it was reported that the attackers took home more than $9 million in double spend transactions. This loss was borne by crypto exchange OKEx; platform users did not endure any loss due to OKEx’s user-protection policy.
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Summary # In Jan 2020, the Bitcoin Gold (BTG) blockchain was hit by a 51% attack, resulting in a loss of over $70,000 worth of BTG. The attack lasted for two days, during which time the attackers were able to double-spend coins.
Attackers # It is still unclear who the attackers were, but it is believed that they rented computing power from cloud mining services to gain control of the BTG network.
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Summary # Bitcoin Cash (BCH) faced a 51% attack on May 15, 2019, in which a group of miners controlled the majority of the network’s hash power. Rather than an attempt at theft or network disruption, this was a unique situation where the miners intervened to prevent a malicious entity from exploiting a network upgrade to insert invalid transactions. The mining pools, BTC.com and BTC.top, spearheaded the move to protect the network’s integrity.
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Summary # Ethereum Classic, a well-known cryptocurrency, experienced a 51% attack in January 2019. The attackers managed to double-spend ETC coins and caused significant losses for users and exchanges.
Attackers # The identity of the attackers behind the Ethereum Classic 51% attack remains unknown. It is suspected that the attackers rented the required hash power from mining marketplaces, such as NiceHash, instead of owning and operating the necessary mining hardware themselves.
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Summary # In November 2018, AurumCoin (AU), a relatively lesser-known cryptocurrency, was hit by a 51% attack. During the attack, an anonymous entity was able to gain control of a majority of the network’s hash rate, which enabled them to alter the blockchain ledger and perform double-spend transactions. The attack resulted in the loss of 15,752.26 AurumCoins from the Cryptopia exchange, which was valued at approximately $500,000 at the time.
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Summary # Vertcoin, a cryptocurrency that focuses on decentralization, was hit by a 51% attack in October 2018. The attack led to double-spending and the loss of thousands of dollars in assets. The attackers took advantage of the Lyra2REv2 algorithm, which was susceptible to NiceHash-driven attacks due to the availability of hash power for rent. In response to the attack, Vertcoin switched to a new algorithm called Verthash, which aimed to provide better security against similar attacks in the future.
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Summary # On June 2, 2018, ZenCash, now known as Horizen (ZEN), fell victim to a 51% attack. During this attack, the perpetrator managed to double-spend ZEN coins by gaining control of a majority of the network’s hashrate. The attack lasted several hours and resulted in an estimated loss of approximately 23,000 ZEN, which was equivalent to about $550,000 at that time.
Attackers # The identity of the attacker or attackers who conducted the 51% attack on the ZenCash network remains unknown.
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Summary # Bitcoin Gold was hit by a 51% attack on May 19, 2018. The attackers were able to double-spend 388,000 BTG, worth around $18 million at the time of the attack. Affected exchanges included Bitinka, Bithumb, Coinnest, Bittrex, and Bitfinex, while wallets such as the official Bitcoin Gold wallet and Ledger wallet were also impacted. As a result of the attack, Bitcoin Gold’s value dropped from around $60 to $30 per coin.
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Summary # Verge blockchain fell victim to a hybrid attack, which combined a mining algorithm exploit with a 51% attack. Attackers exploited vulnerabilities in Verge’s mining algorithm and a bug in the retargeting mechanism, allowing them to mine blocks rapidly and accumulate approximately 250,000 XVG coins, worth $1.75 million. The attack began on April 4, 2018, and despite the Verge development team’s attempts to release patches, the issue persisted until April 9, 2018, when a second patch finally resolved the problem.
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