Bitcoin Forum

My questions are regarding the level of security endowed within Bitcoin.
Has there ever been a 51% on Bitcoin's network? I understand that as more miners enter the network, the greater the hash rate meaning the more difficult it is to perform an attack. This also means that it was much easier to perform the attack during the early years of Bitcoin, that's when it was most vulnerable. Was there any attack in the early years of Bitcoin and how much would it cost now to perform a 51% attack?

$500,000 per hour just for electricity and $1 billion in equipment. It's not worth it.
Back in 2014, GHash had reached something like 40% of all power and people started to complain on Twitter/FB. Then miners moved to other places. After this GHash published a PR to say they had no intention for a 51% attack.

No, the bitcoin blockchain has never been successfully attacked with a 51% attack. There have been concerns over miners controlling a large share of hash power and thus launching an attack, but the Chinese clampdown on mining has helped to lessen the concentration of miners in China. Every day that bitcoin survives it gets stronger.

At some point, almost is perhaps the term because I couldn't remember any instance that such an attack was successful. Well back in 2014-2016, people were concerned about the growing number of miners in China, and also their hash rate at one time exceeded 50% which was near the said attack. Thankfully though these Chinese miners don't want to ruin the network and it has been clear since then that they have no intention to do so, given that A: they are different miners controlled by different operators and B: mining back then was so profitable that destroying the network is literally closing the gold mine away.

I don't think we had a 51% attack on bitcoin as such.
Once in 2014 a mining pool called Ghash.io reached above 50% of total mining power and as the community was concerned about the risks of a single pool having more than 50% of hashes, the pool Ghash.io voluntarily lowered it's bitcoin mining power below 40%.

Unlike BCH and Ethereum Classic (these two are the most famous) Bitcoin has never experienced a 51% attack. Back in 2013 or 2014 there were some concerns raised by the community on social media about a mining pool gaining a large portion of Bitcoin hash, but it was controlled later on. It is not worth trying to do the same now as the cost of mining has risen up drastically.