How nodes secure the blockchain

[Obi theo]

Going through an article, I found out a very interesting facts that I would love to share with all ,
 NODES :
Nodes are we know is a part of the blockchain that store data , meaning that the blockchain exist as nodes.
But I am here to inform you of how the blockchain is secure by nodes
 Nodes can be online or offline. Online nodes are receiving, saving and broadcasting all the latest blocks of transactions from and to other nodes, while offline nodes do not. When an offline node comes back online, it will need to catch up with the rest of the blockchain first by downloading all blocks that were added to the blockchain ever since the node went offline. This process is often referred to as synchronizing with the blockchain.
Image for post.
Source :
https://medium.com/coinmonks/blockchain-what-is-a-node-or-masternode-and-what-does-it-do-4d9a4200938f

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[ranochigo]

Blockchain is a ledger. Nodes are decentralized mechanism to distribute it.

Nodes doesn't technically secure the entire system but rather it acts as a decentralized storage for the blockchain where every nodes saves their own copy. It doesn't necessarily mean that they would provide security for the blockchain though. Verifying the entire blockchain primarily benefits the user of that node and the people retrieving data from that node. Having more nodes does however means that sybil attacks are harder due to the larger number of nodes to choose from.

[hd49728]

The healthy of the network depends on the total hashrates and how decentralized it is. Nodes are backup of blockchain database and different nodes update their database at different times. Some nodes update it 24/7, but some nodes do it not too often (online and offline depend on times).

Nodes can also help to detect strange things from other nodes.

Mastering bitcoin, the Bitcoin network, chapter 8

[Little Mouse]

Nodes are backup of blockchain database and different nodes update their database at different times.

Is it like if there are more full nodes, there is less chance of 51% attack? I'm little bit confused on this. I mean 51% attack depends on number of full nodes and frequency of them being individual or not? Or this is totally different from full node?