What Is A Sybil Attack in Blockchain?

What Is A Sybil Attack?

"Sybil" originated from "Sybil Dorsett", a woman with Dissociative Identity Disorder, a classical psychological disease, known as Multiple Personality Disorder. A "Sybil attack" means an individual or organization manipulates or controls a P2P online network system by creating and using multiple accounts(fake identities), or blockchain nodes. In the world of crypto, a Sybil attack is generally one person running multiple nodes to get more centralized power, and influence the vote in governance.

How Does a Sybil Attack Work?

On the blockchain network, the operations are decentralized and distributed. The nodes are separated around the world and controlled by different identities. This kind of design makes the network secure and stable. Then if a large part of nodes are controlled by the same person who remains in the shadows, so the network decisions can be influenced. For example, if the decisions of one crypto project are voted by nodes on the network, then an attacker can create thousands of fake accounts to influence the decisions.

What Results Can Sybil Attacks Cause?

The results caused by Sybil attacks can be serious for blockchain:

• A 51% attack. While Sybil attackers control the majority of the network computing power or hash rate, they can start a 51% attack. They can change the order and reserve transactions, then "double spending" may happen.
• Out-vote the honest nodes on the network if they create enough Sybil identities. They can then refuse to receive or transmit blocks and other users will be blocked from a network.

Is Sybil Attack Possible in Bitcoin?

It is very difficult to attack via Sybil in Bitcoin, basically impossible. The reason is Bitcoin use "Proof of Work" consensus, you must actually own the computer power required to create a new block and that makes it difficult and costly for an attacker. Also, the number of miners is large, it is not possible to control more than 51% of miners. However, other blockchain networks with less hash rate backing may be susceptible to a Sybil attack. Ethereum Classic(ETC) is one of the cases that fail to prevent Sybil attacks. An attacker purchased the hash rate for less than $200,000 and gained majority control over the Ethereum Classic mining network.

How to Prevent Sybil Attacks?

Well, as a user, Sybil attacks are not what we can prevent. It is the developers' responsibility to prevent Sybil attacks. They may use the following measures:

• Use "mining" to prevent Sybil attacks. Such as Bitcoin uses proof-of-work consensus algorithms, and users have to expend energy to mine. To make a Sybil attack realize, people need to purchase a large sum of mining equipment. The cost is large and the costs associated with such an attack would be unreasonable.
• Make it easy to create blockchain nodes to prevent Sybil attacks. For most networks, it is easy to be the node of the blockchain. They are low-cost and able to be operated by anybody with an internet connection. So it is difficult for attackers to control most of the network's nodes since there are too many and are distributed across the world.
• Use a validation system to prevent Sybil attacks. A lot of platforms will use IP address validation, and two-factor authentication to prevent someone from controlling multiple accounts.

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