📌 51% Attack Summary

A 51% attack is a situation where a single person or group gains control of more than half of the computing power on a blockchain network. With this majority, they can manipulate the system by reversing transactions or blocking new ones from being confirmed. This threatens the security and trustworthiness of the blockchain, as it allows dishonest behaviour like double spending.

🙋🏻‍♂️ Explain 51% Attack Simply

Imagine a classroom where the majority decides the rules. If over half the students team up, they could change grades or ignore fair play. Similarly, a 51% attack lets someone with most of the power control the blockchain, breaking its fairness and trust.

📅 How Can it be used?

When building a blockchain project, it is crucial to design safeguards against any one party gaining more than half the network’s power.

🗺️ Real World Examples

In 2019, the Ethereum Classic blockchain experienced a 51% attack, allowing attackers to reorganise the blockchain and double spend coins, which caused exchanges to lose funds and trust in the network to drop.

A smaller cryptocurrency called Bitcoin Gold suffered a 51% attack in 2018, where attackers gained enough mining power to reverse transactions and steal funds from exchanges, resulting in losses for both users and platforms.

✅ FAQ

A 51% attack happens when someone controls more than half of the computing power on a blockchain network. This gives them the ability to change the order of transactions or even reverse them, which means they could spend the same coins twice. It undermines the fairness and reliability that blockchains are supposed to offer.

A 51% attack is a big deal because it puts the whole system at risk. If someone can rewrite transaction history or block new transactions, it makes people lose trust in the network. This could cause the value of the cryptocurrency to fall and make people wary of using it.

While a 51% attack is possible on any blockchain, it is much harder to pull off on large networks with a lot of participants. Smaller blockchains with fewer people mining or validating transactions are more vulnerable because it takes less computing power to reach that majority.

📚 Categories

• Anti Attack
• Blockchain
• Threat Detection and Response

🔗 External Reference Links

51% Attack link

👏 Was This Helpful?

If this page helped you, please consider giving us a linkback or share on social media! 📎 https://www.efficiencyai.co.uk/knowledge_card/51-attack

Ready to Transform, and Optimise?

At EfficiencyAI, we don’t just understand technology — we understand how it impacts real business operations. Our consultants have delivered global transformation programmes, run strategic workshops, and helped organisations improve processes, automate workflows, and drive measurable results.

Whether you're exploring AI, automation, or data strategy, we bring the experience to guide you from challenge to solution.

Let’s talk about what’s next for your organisation.

---

💡Other Useful Knowledge Cards

Homomorphic Encryption

Homomorphic encryption is a type of encryption that allows data to be processed and analysed while it remains encrypted. This means you can perform calculations or run programmes on the encrypted data without needing to decrypt it first. The results, once decrypted, match what you would get if you had performed the same operations on the original, unencrypted data.

AI for Supply Chain Resilience

AI for supply chain resilience refers to the use of artificial intelligence tools and techniques to help supply chains withstand and quickly recover from disruptions. These disruptions can include natural disasters, sudden changes in demand, or problems with suppliers. By analysing large amounts of data and making predictions, AI can help businesses identify risks, optimise routes, and make faster decisions to keep products moving. This technology helps companies maintain stable operations, reduce delays, and minimise losses when unexpected events occur.

Token-Based Incentives

Token-based incentives are systems where people earn digital tokens as rewards for certain actions or contributions. These tokens can hold value or provide access to services, special features, or voting rights within a project or platform. The approach encourages positive behaviour and participation by making rewards easy to track and transfer.

Function as a Service

Function as a Service, or FaaS, is a cloud computing model where you can run small pieces of code, called functions, without managing servers or infrastructure. You simply write your code and upload it to a cloud provider, which takes care of running it whenever it is needed. This allows you to focus on your application logic while the cloud provider automatically handles scaling and resource management.

Digital Rights Platform

A digital rights platform is an online system or service that helps creators, rights holders, and organisations manage, protect, and distribute their digital content. It tracks who owns what content, handles permissions, and automates licensing or payments. These platforms are used for music, videos, images, books, and other digital media to ensure creators are paid and content is used legally.