## What Happens When Miners Control the Blockchain? Understanding 51% Attack Risks

A 51% attack represents one of the most critical vulnerabilities in blockchain networks. This type of assault occurs when a single entity or coordinated group gains control over more than half of the network's mining hashrate or computational power—essentially seizing the ability to dictate blockchain operations.

### How the Attack Works

Once attackers command the majority hashrate, they gain unprecedented control over transaction processing. They can choose which transactions get included in blocks, determine their sequence, and even reverse completed transactions. This capability enables double-spending: sending the same cryptocurrency twice by manipulating the transaction history. The attacking miners essentially become the arbiters of the network's truth, overriding the consensus mechanism that normally protects blockchain integrity.

### Cascading Consequences

The implications extend far beyond transaction manipulation. A successful assault can inflict severe denial of service on regular blockchain users, paralyzing the network's functionality. Beyond disrupting operations, attackers holding mining majority can:

- Alter block rewards, redistributing mining incentives
- Mint new tokens outside the protocol's intended supply
- Execute large-scale theft by transferring tokens at will
- Erode user confidence in the network's security

Bitcoin and other proof-of-work blockchains remain theoretically vulnerable to this threat, though the prohibitive cost of acquiring 51% of hashrate on major networks makes such attacks practically challenging on established chains.

### Why It Matters

Understanding 51% attack mechanisms is essential for evaluating blockchain security. While major networks have proven resilient through distributed mining, smaller or newly launched blockchains require careful monitoring of hashrate distribution to prevent concentrated power from enabling such attacks.