51% Attack Examples – Real-World Cases & Lessons

When talking about 51% attack examples, situations where a single miner or group controls more than half of a blockchain's hash power, enabling them to rewrite transaction history. Also known as a majority attack, this threat shows how decentralization can be challenged. Blockchain networks rely on distributed consensus, but when the balance tips, the attacker can double‑spend or censor users. Understanding these incidents helps anyone building or using crypto stay one step ahead.

One classic double‑spend scenario happened on a small proof‑of‑work coin in 2018. The attacker rented enough mining power to exceed 51% of the network, reversed a high‑value transaction, and walked away with the original funds. A similar pattern appeared on an older Bitcoin fork in 2020, where a coordinated pool briefly overtook the hash rate, delayed confirmations, and forced exchanges to halt withdrawals. These cases illustrate the semantic triple: 51% attack examples require majority hash power, which influences the ability to double‑spend in proof‑of‑work systems.

Beyond mining, proof‑of‑work itself shapes vulnerability. Coins with low total hash rates are easier targets, while those with robust, diverse miners are harder to compromise. The principle is clear: the more distributed the work, the lower the chance a single actor can achieve a 51% share. This relationship forms another triple: Proof‑of‑work determines the security level of a blockchain, which directly affects its exposure to majority attacks. Security‑focused developers often add checkpoints or switch to hybrid consensus models to mitigate risk.

What You’ll Find Below

Below is a curated list of articles that dive deeper into each incident, explain the technical tricks used, and share practical steps you can take—whether you’re a trader, developer, or just curious about crypto safety. From detailed post‑mortems of past attacks to guides on strengthening your own projects, the collection covers a wide range of perspectives. Keep reading to see how real‑world examples shape today’s best practices in cryptocurrency security.