CoinWallet.eu's 2015 Bitcoin Stress Test Cost $49,000

In 2015, an entity known as CoinWallet.eu launched a series of attacks on the Bitcoin network, aiming to demonstrate the vulnerabilities of its 1MB block size limit. The group executed what they called the “Ultimate Bitcoin Stress Test,” flooding the network with dust transactions to fill each block to capacity. This action was intended to drive up fees and increase wait times for legitimate users, thereby proving that the block size limit was insufficient.

The first attack, which took place in June 2015, failed to achieve its intended effect. Despite spending 2 BTC, equivalent to $500 at the time, the servers crashed under the weight of a mempool that was only 12MB, far short of the 241MB backlog they had aimed for. The second attack, launched five days later, was more successful and managed to convince some users that the large blockers might have a valid point.

The third wave of attacks, occurring between July 7 and 11, resulted in a significant backlog of transactions, ranging from 27,000 to 80,000. The attackers spent 30 BTC, worth $8,000 at the time, to flood the network. This attack was particularly notable for its use of dust transactions sent to well-known wallets and generic public key addresses. The fourth and final attack in September involved posting thousands of private keys to Bitcointalk, each corresponding to an address containing a slice of 200 BTC. Users rushed to collect the free coins, submitting 90,000 transactions, many of which were related to the same bitcoin and could be easily discarded by miners.

Despite the initial chaos, the actions of miners, pools, and key players, including Gregory Maxwell, mitigated the adverse effects of the attacks over a short period. The situation highlighted the ongoing debate over transaction filtering and the role of node runners in suppressing spam. The academic study concluded that a little less than a quarter of transactions across a 10-day period at the peak of the campaign were spam, increasing fees by 51% and processing delays by seven times.

The total cost of the four attacks was approximately $49,000 worth of bitcoin in 2015. Today, with bitcoin at all-time highs, those 201 BTC would be worth almost $24 million, equivalent to a jackpot lottery prize. This incident underscores the resilience of the Bitcoin network and its ability to withstand significant attacks, even when executed with substantial financial resources.