Understanding 51% Attacks

51% attacks refer to a potential assault on a blockchain network, where a single miner or a group of miners attain control over more than 50% of a network's mining hash rate or computing power. This hash rate is what is required to complete the complex mathematical equations necessary to validate transactions and add them to the blockchain. Attaining over half the power gives the entities unfair and potentially damaging control over the network.

The primary risk of a 51% attack springs from the inherent principle of blockchain's consensus mechanism. In most blockchains like Bitcoin, the protocol follows the longest chain rule, meaning that the chain with the most blocks will be considered by the network as the truth. Therefore, if an entity controls more than 50% of the hash rate, they can outpace other miners in new block creation and eventually create the longest chain.

A party that executes a 51% attack can carry out double-spends, where they spend a single transaction twice. First, they conduct a transaction that goes into the official blockchain. Next, they use their majority control to form an alternative, private blockchain where the same transaction does not exist. By outpacing the official blockchain, their private chain becomes the longest chain which the network accepts. As a result, the original transaction is wiped out, and they can use the same currency again.

However, it must be noted that a 51% attack does not provide control of the actual blockchain coding or the ability to alter old transactions—just a chance to double-spend and manipulate the record-keeping of recent ones.

Executing a 51% attack is difficult and costly. It involves acquiring more computational power than the remaining network combined, requiring high costs for purchasing and running the right hardware, not to mention the significant electricity usage. Given that the Bitcoin network, for example, has thousands of miners worldwide, overpowering such a network is challenging and financially draining.

Moreover, successful 51% attacks detriment the attacker's long-term potential profits. When an attack is detected, confidence in the blockchain’s security drops sharply—often leading to a drop in the asset's value. So, while one might have more blocks to mine, the rewards might be less worthy in real-world value. Additionally, changes to protocols and increased network decentralization have made these attacks even harder to execute successfully.

Despite this, smaller, lesser-known blockchains are often more vulnerable to 51% attacks, as they have a lower hash rate overall, making it less resource-draining to gain a majority control. While it’s less lucrative than attacking larger chains, such maneuvers can still yield gains that exceed the resource cost deployed for the attack.

In conclusion, a 51% attack is a potential but unlikely threat to blockchain networks. While it is indeed a fundamental vulnerability that arises from the mechanism of blockchain technology itself, the high costs of launching such an attack on a large, secure blockchain network like Bitcoin or Ethereum act as significant deterrents. Nonetheless, the crypto-community continually works on measures to mitigate this risk, ensuring a secure environment for transactions and maintaining the intrinsic value of blockchain technology.