Securing Blockchain Networks like Ethereum and Hyperledger Fabric

The majority attack

Also known as a 51% attack, this is a particular type of Sybil attack that is achieved when the attacker controls 51% of the mining capacity, which is determined by the network's hash rate.

Controlling more than 50% of the hash rate means being able to control the consensus needed to create new blocks in the blockchain, as well as exercising control over the inclusion, exclusion, and ordering of the corresponding transactions.

The 51% attack allows the attacker to do the following:

• Slow down the inclusion of transactions awaiting confirmation
• Modify or replicate existing transactions by performing double-spending attacks
• Split the blockchain by forking it

However, the attacker is not able to insert invalid transactions ...