The ETC Double-Spend Incident: What Happened?
In early January, Ethereum Classic (ETC) faced a suspected 51% attack, with major exchanges like Coinbase, Coincheck, and bitFlyer reporting double-spending transactions across multiple block heights. Blockchain security firm PeckShield identified 15 suspicious transactions between January 5–8, resulting in losses of 219,500 ETC (~$1.1 million).
Initial reports suggested the attack cost merely **$20,000**, yielding **10x returns** by double-spending 54,200 ETC (~$270,000) within four hours. But how accurate is this claim?
Calculating the True Cost of a 51% Attack
The Crypto51.app Misconception
While crypto51.app estimates hourly attack costs at:
- ETC: $4,528/hour
- BTC: $285,244/hour
- ETH: $99,349/hour
These figures are misleadingly low for sustained attacks. For context, a 4-hour BTC attack would theoretically cost ~$1 million—trivial for a $700B network. Large blockchains deter attacks through prohibitively high costs, making such events statistically improbable.
Real-World Attack Mechanics
To execute a 51% attack, attackers must control >50% of the network’s hashrate. Two primary methods exist:
Co-opt Existing Miners
- Difficult due to decentralized miners prioritizing steady earnings over risky double-spending.
- Successful attacks often crash coin values, harming miners’ long-term interests.
Rent New Hashpower
- Platforms like NiceHash allow short-term hashrate rentals.
- ETC’s vulnerability: NiceHash offers 100% rentable hashrate for ETC, unlike BTC/ETH.
👉 Why smaller chains like ETC are prime targets for 51% attacks
Revised Cost Estimate for ETC’s Attack
PeckShield’s data reveals the attack spanned 4 days, with 100+ block reorganizations. Factoring in:
- Hidden attempts: Failed attacks leave no on-chain traces.
- Setup time: Days of debugging often precede actual attacks.
Actual Cost:
$4,528/hour × 24 hours × 4 days = **$434,688** (conservative estimate).
Profit: ~$270,000 (far below the alleged 10x return).
Why Bitcoin Remains Unhackable
Attempting a BTC 51% attack requires:
Hardware Costs
- 40.3 EH/s needed (BTC’s current hashrate).
- Using Antminer S9s (14 TH/s @ $400/unit): ~$1.15B upfront.
Operational Costs
- 7-day attack duration: +$19.6M in electricity (@ $0.03/kWh).
- Total: $11.7B+—economically unviable.
👉 Explore how top blockchains mitigate 51% risks
Key Takeaways
- Small Chains = High Risk: ETC’s lower hashrate makes it susceptible to rented attacks.
- BTC/ETH Security: Their size and decentralization create $Billion+ attack barriers.
- Investor Caution: Holders of forked/small-cap coins should assess 51% attack risks.
FAQ: Understanding 51% Attacks
Q: Can exchanges prevent double-spending losses?
A: Yes—by increasing confirmation requirements for deposits (e.g., 100+ blocks for ETC).
Q: How often do 51% attacks occur?
A: Rarely on large chains. ETC suffered 3+ attacks since 2019 due to its modest hashrate.
Q: Does proof-of-stake (PoS) eliminate this risk?
A: Mostly. PoS replaces miners with validators, making attacks costlier via slashed stakes.
Q: What’s the cheapest chain to attack today?
A: Check crypto51.app for real-time rankings—but remember hidden costs apply.
Q: Can ETC prevent future attacks?
A: Possible solutions include checkpointing or merging with a larger PoW chain (e.g., ETH).
Final Thoughts
While $20,000 ETC attacks are exaggerated, smaller chains remain vulnerable. Investors should prioritize well-secured blockchains to mitigate double-spend risks. For deeper insights, consult our analysis on emerging blockchain security frameworks.