Attacking Bitcoin Costs Hundreds of Millions an Hour — Attacking Ethereum Classic Costs Under $15,000

A 51% attack happens when a single actor or group gains control of most of a network's hash rate. It does not reach other people's transactions: the attacker can only reverse their own recent ones and spend the same coins twice, as Binance Academy sets out.

The cost of pulling this off varies wildly between networks. For Bitcoin, a one-hour attack would run into the hundreds of millions of dollars — the network is simply too large to touch. For Ethereum Classic (ETC), a top-cap PoW coin, a one-hour attack costs under $15,000; for Litecoin, it's $75,000-90,000 an hour, KuCoin notes.

Why smaller networks are so cheap to attack: hash-rate rental marketplaces let attackers rent computing power for a few hours instead of buying hardware outright. If a small blockchain uses a common algorithm like SHA-256, an attacker can rent enough power to temporarily outweigh the entire network.

What this means in practice: Ethereum Classic has already suffered successful 51% attacks in 2019 and 2020, costing exchanges millions through double-spending. The rule is simple: the smaller a network's hashrate (or staked capital), the cheaper it is to cheat — and that applies to nearly every coin outside the top two by market cap.

This article is for informational purposes only and does not constitute investment advice.