The 2015 Spam Attacks: Lessons in Bitcoin’s Resilience and Debate

In the summer of 2015, Bitcoin faced a series of disruptive spam attacks that tested the network’s resilience and reignited debates over its future. These attacks, orchestrated by CoinWallet.EU, aimed to stress test Bitcoin’s limits and push for a change in its blocksize policy.

• Spam attacks disrupt Bitcoin in 2015
• CoinWallet.EU’s stress test
• User experience and fees impacted
• Miners and Bitcoin Core’s response
• Blocksize War intensified
• Lessons for today’s debates

The first wave of spam hit Bitcoin in June 2015, but it was the July onslaught that truly shook the network. Over 80,000 unconfirmed transactions piled up, creating a digital traffic jam. CoinWallet.EU, claiming to be based in London, called these attacks a “stress test.” Their objective was to expose the limitations of Bitcoin’s 1MB blocksize limit and advocate for an increase to deter future spam attacks.

The user experience during these attacks was akin to trying to get through a crowded concert with everyone pushing and shoving to reach the front. Transactions were stuck in limbo for hours, and fees skyrocketed as users scrambled to get their transactions processed. A mempool, which is a holding area for unconfirmed transactions, was overwhelmed, much like a postal service flooded with junk mail.

Miners, the backbone of Bitcoin’s network, responded swiftly. They adjusted their policies, with some increasing the blocksize limit to 1MB and others raising the minimum relay fee—the fee required for a transaction to be relayed across the network. Bitcoin Core, the primary software implementation of Bitcoin, introduced mempool limits and increased the default mempool size to combat the chaos. These changes were like turning up the volume to drown out the noise of spam.

These attacks didn’t just cause disruption; they reignited the fiery debate known as the Blocksize War. Large blockers, who advocated for a larger blocksize to improve scalability and reduce transaction spam, used the attacks as evidence to support their argument. Mike Hearn, a Bitcoin developer and large blocker, argued, “The best defence against this is to make it as expensive as possible, by increasing the block size limit.” On the other hand, small blockers, who prioritized network security and decentralization, remained steadfast in their opposition. Luke-Jr, a prominent developer, emphasized, “Bitcoin has miners and the block size limit specifically to combat these kinds of attacks.”

An academic study later found that 23.41% of transactions during the peak of the attack were spam, which increased average fees by 51% and processing delays by 7 times. This was a clear signal that Bitcoin’s infrastructure needed to evolve, like a city expanding its roads to handle increased traffic.

The 2015 spam attacks are more than just a historical footnote. They offer valuable lessons for today’s debates over Bitcoin’s transaction policies, such as the OP_Return relay limit and handling of potential spam. The attacks demonstrated that significant disruption was possible with a relatively small financial investment, prompting ongoing discussions about how to fortify the network. Imagine trying to get your package delivered during the holiday rush, but instead of festive cheer, you’re dealing with a network meltdown.

The identity of CoinWallet.EU remains a mystery, shrouded in speculation. Some have pointed to connections with Gerald Cotton, the former CEO of Quadriga, and James Wilson, allegedly involved with the company. Yet, concrete evidence remains elusive, leaving us with more questions than answers about the motivations behind the attacks.

As we navigate Bitcoin’s evolving landscape, these attacks remind us of the delicate balance between scalability and security, decentralization and efficiency. They underscore the importance of robust policies and the community’s resilience in the face of adversity. Whether you’re a Bitcoin maximalist or believe in the role of altcoins and other blockchains, these events highlight the shared goal of creating a more secure and efficient financial future.

So, what can we learn from the 2015 spam attacks?

• What were the motivations behind the 2015 Bitcoin spam attacks?

  The attackers, CoinWallet.EU, aimed to demonstrate the limitations of Bitcoin’s 1MB blocksize limit and push for an increase to make spam attacks more expensive and less impactful on the network.

• How did the Bitcoin community and miners respond to the 2015 spam attacks?

  The Bitcoin community and miners responded by adjusting policies to increase the blocksize limit to 1MB, raising the minimum relay fee, and introducing mempool limits to combat spam.

• What were the technical and policy changes that followed the 2015 spam attacks?

  Technical changes included the introduction of mempool limits and an increase in the default mempool size in Bitcoin Core. Policy changes saw miners increase their blocksize limit to 1MB and a fivefold increase in the minimum relay fee.

• How did the 2015 spam attacks influence the blocksize debate?

  The attacks intensified the blocksize debate, with large blockers using the degraded user experience as evidence to support their argument for increasing the blocksize limit, while small blockers remained steadfast in their opposition.

• What lessons can be learned from the 2015 spam attacks for current Bitcoin policy debates?

  The 2015 attacks illustrate that spam attacks are not new and highlight the importance of robust policies to manage spam. They also show the potential for significant disruption with relatively small financial investment, prompting ongoing discussions about transaction policies and the handling of potential spam.

“Bitcoin is at a breaking point, yet the core developers are too wound up in petty arguments to create the required modifications for long term sustainability.” – CoinWallet.EU

“Bitcoin has miners and the block size limit specifically to combat these kinds of attacks.” – Luke-Jr

“The best defence against this is to make it as expensive as possible, by increasing the block size limit.” – Mike Hearn

“A valid TXN is a VALID txn. Full stop. End of story. NO POLITICS.” – spartacusrex

“We have presented an empirical study of a spam based ‘stress test’ DoS attack against Bitcoin.” – Academic paper