All these nodes in this network create a consensus. They agree | 𝘾𝙔𝘽𝙀𝙍 𝙏𝘼𝙇𝙆 ™ 😷 𝗛𝗮𝗰𝗸𝗶𝗻𝗴 𝗧𝗼𝗼𝗹𝘀 . 𝙇𝙚𝙖𝙠𝙨 & 𝙈𝙤𝙧𝙚

All these nodes in this network create a consensus. They agree about what blocks are valid and which are not. Nodes in the network will reject blocks that are tampered with.
So, to successfully tamper with a blockchain

You will need to tamper with all blocks on the chain

Redo the proof-of-work for each block

Take control of greater than 50% of the peer-to-peer network.

After doing all these, your tampered block becomes accepted by everyone else. This is next to an impossible task. Hence, Blockchains are so secure. Next, in this beginner’s Blockchain development tutorial, we will learn how a Blockchain transaction works?