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51% attack


A 51 percent attack (or majority attack) occurs when a malicious user or group of users gain control of more than 50% of the blockchain’s hash rate (computing power), causing network disruption. 

Understanding the term

Blockchain technology comes with inherent security protocols. A 51% attack takes over the protocols by overruling an existing blockchain network and harming its integrity. The malicious agents can stop the confirmation of transactions and reverse them. This can lead to double-spending — the same unit of the currency to be spent twice — of the cryptocurrency associated with the blockchain. Depending on the mining power of the attacker, the attack’s impact can be mild or more consequential. 

In a 51% attack on Bitcoin, the blockchain’s network gets affected, allowing the attackers to cause network disruptions and process transactions faster than the honest nodes (miners). The risks associated with such attacks can compromise user and miner confidence, cause loss of digital assets, and raise concerns about the reliability, security, and trustworthiness of blockchain technology. 


In growing technologies like blockchain and cryptocurrency, 51% attacks always remain a possibility. Defending against these types of attacks would require community members to support decentralization and uphold immutability, which are two aspects we can expect from upcoming technology.

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