51% Attack: What It Is, How It Works, and Why Blockchain Security Matters
When someone controls more than half of a blockchain’s computing power, they can pull off a 51% attack, a scenario where a single entity or group dominates the network’s validation process, allowing them to reverse transactions, block new ones, or double-spend coins. Also known as a majority attack, this isn’t science fiction—it’s a real threat to smaller blockchains that lack enough miners or stakers to stay secure. The bigger the network, the harder it is to pull off. Bitcoin’s network hash rate, the total computational power used to mine and secure Bitcoin, is over 600 exahashes per second. That’s more than the combined power of the top 100 supercomputers on Earth. Trying to out-mine that is like trying to outrun a jet with a bicycle.
Most Proof of Work, the consensus mechanism that lets miners compete to add blocks to the blockchain using computational power blockchains are vulnerable if their mining power is too concentrated. Smaller coins like Verge, Bitcoin Gold, and Ethereum Classic have been hit before. In each case, attackers rented mining power from services like NiceHash, briefly took over the network, and double-spent millions. Meanwhile, cryptocurrency consensus, the system that ensures all participants agree on the state of the ledger in Proof of Stake chains like Ethereum works differently—there’s no mining, so you can’t rent hash power. Instead, attackers would need to buy and lock up over half of all the staked ETH, which would cost billions and destroy the value of their own holdings.
That’s why Bitcoin’s security isn’t just about technology—it’s about economics. The more people mine, the more expensive an attack becomes. And the more expensive it is, the less likely anyone will try. This is why the 51% attack is rare on big networks but common on ones with low hash rates and thin trading volumes. If you’re holding a coin with low market cap and few miners, you’re not just gambling on price—you’re gambling on whether its network can defend itself.
What you’ll find below are real-world examples of what happens when networks fail to stay secure. From shady exchanges with fake trading volumes to meme coins with no real tech, these posts show you how to spot the weak links before you invest. You’ll learn which projects are just pretending to be decentralized, which ones have real mining power behind them, and how to avoid becoming a victim of a blockchain that’s too small to protect itself.