What is a Sybil Attack?

Phishing attack is a form of security threat on an online system, when someone tries to take control of the network by creating multiple accounts, nodes or computers.

This type of attack could be as simple as someone creating a bunch of social media accounts.
But in the world of cryptocurrencies, a more precise example is when someone operates multiple nodes on a blockchain network.

The word “Sybil” in the name of this attack comes from the case of a woman named Sybil Dorsett who was treated for Split Identity Disorder – also known as Multiple Personality Disorder.

What problems can phishing attacks cause?

An attacker can win more votes than real nodes on the network if they generate enough fake identities (or Sybil identities). They can then refuse to receive or send blocks and succeed in blocking other users from the network.

In very large-scale impersonation attacks, when an attacker controls most of the network’s computing power or hash rate, they can perform a 51% attack. In those cases, they can change the order of transactions, and not confirm transactions. They can even reverse transactions they made when they took control, which could lead to double consumption.

Over the years, computer scientists have spent a lot of time and research trying to find ways to detect and prevent phishing attacks with varying degrees of success. Currently, there is no guaranteed defense against these attacks.

So how can blockchain mitigate Sybil attacks?

Many blockchains use different “consensus algorithms” to help defend against spoofing such as Proof of Work, Proof of Stake, and Delegated Proof of Stake.

These consensus algorithms don’t actually prevent impersonation attacks, they just make it impractical for an attacker to successfully execute a spoofing attack.

For example, Bitcoin’s blockchain applies a specific set of rules to the creation of new blocks.

One of the principles is that the ability to generate new blocks should be proportional to the total processing power of the Proof of Work mechanism. That means you have to actually own the computing power needed to create a new block, which is very difficult and expensive for an attacker.

Since Bitcoin mining is so profitable, miners have a great incentive to mine honestly, instead of trying to do a spoofing attack.

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