What is a 51% Attack?

And Why Crypto Miners Should Care – Especially in Canada

If you’re just getting started with crypto mining in Canada, you’ve probably come across terms like proof-of-work, mining pools, and maybe even 51% attack. That last one sounds a little ominous—and for good reason. A 51% attack is one of the biggest threats to blockchain networks, especially smaller ones.

So what is it, how does it work, and why should miners (even small home-based rigs like mine) care?

The Basics: How Blockchains Stay Secure

Let’s start with the good news: blockchains like Bitcoin and Ethereum (when it was proof-of-work) are designed to be incredibly secure. They rely on a decentralized network of miners to validate transactions and add new blocks to the chain.

Each miner contributes computational power—hashrate—to help solve complex mathematical puzzles. The more hashrate a network has, the more secure it becomes.

Enter the 51% Attack

A 51% attack happens when a single miner, or group of miners working together (usually in a mining pool), controls more than 50% of the total hashrate of a blockchain. That majority gives them an unfair advantage.

Here’s what an attacker with 51% power could do:

Double spend coins (basically spend the same crypto twice)
Prevent new transactions from confirming
Block other miners from finding valid blocks
Rewrite parts of the blockchain to favor themselves

They can’t create new coins out of thin air or steal from your wallet directly—but the consequences are still massive for trust and price stability.

Why This Matters for Canadian Miners

Here in Canada, we have a unique opportunity for low-cost mining thanks to our cold climate and relatively cheap hydroelectric power in places like Manitoba and Quebec. That’s great for small-scale miners—but it also means we might be attracted to lesser-known coins that are easier to mine.

Here’s the catch: smaller proof-of-work coins are more vulnerable to 51% attacks because they have less total hashrate securing the network.

If you’re spec mining newer or niche coins like I am, it’s important to be aware of this risk. You could spend days mining a coin, only to see its blockchain compromised and value plummet overnight due to a successful attack.

Real-World Examples of 51% Attacks

Ethereum Classic (ETC) has suffered multiple 51% attacks in recent years, even though it’s a well-known coin.
Vertcoin (VTC) was attacked in 2018 and 2019 due to its relatively low hashrate.
Other smaller coins are regularly targeted by rented hashrate through services like NiceHash.

How to Protect Yourself as a Miner

While you can’t personally stop a 51% attack, you can take steps to protect your efforts:

Research the network hashrate before mining a new coin.
Stick to coins with active development teams and communities.
Spread your mined coins to secure wallets, not just exchanges.
Join mining communities (like Reddit, Discord, or even my blog!) to stay informed.

Final Thoughts

As someone who just started mining from my basement here in Winnipeg, I’m learning as I go. And learning about 51% attacks helped me realize that choosing what coin to mine is about more than just profitability—it’s also about security.

If you’re like me—mining for the fun of it, to learn, and hopefully turn a profit—understanding risks like 51% attacks is key to making smarter decisions.

Got questions? Leave a comment or check out my Beginner’s Guide to Crypto to get started.

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