According to the analytical company Messari, the cost of a successful 51% attack on the Bitcoin blockchain is more than $21 million per day. For comparison, a similar attack on the Ethereum network costs about $2.7 million.
The 51% attack is considered one of the most serious threats to many cryptocurrencies. If one or a group of miners has more than 51% of the computing power, then you can get control of the network with the proof-of-work algorithm (PoW).
To attack the Bitcoin network, you need to have a sufficient amount of mining equipment, which is quite a costly process. However, at the moment, attackers can attack the Bitcoin Cash, Bitcoin SV or Litecoin blockchain for less than $1 million, and an attack on the Ethereum Classic blockchain will cost $326,000 at all.
If an attacker successfully carried out an attack, they can selectively block transactions, cancel existing ones, or even reorganize the blockchain. As a result, you can rewrite previously confirmed blocks and even divide the network into several chains.
For the network to be sufficiently secure, it must be decentralized. In other words, the share of each individual miner should be small. In this case, it will be extremely difficult to combine the capacity, because it is a large time and money cost.
We remind you that similar attacks have already been carried out in the cryptocurrency ecosystem, mainly on small blockchains such as Bitcoin Gold, Verge, Vertcoin and Ethereum Classic. They have a small hashrate and therefore they have become easy and inexpensive prey for hackers.
