What Is a 51% Attack Against the Bitcoin Network?

Blockchain technology is one of the best weapons against a slew of black hat hacker attacks. Blockchain can fight against DDoS attacks effortlessly, and also prevents alterations to the digital ledger that turns it into such excellent record keeping tech.

As revolutionary as blockchain is, there are certain attacks that it really can't work well with. One such attack is a 51% attack, and it could potentially destroy any of the altcoins you want to invest in. If you're wondering what is a 51% attack, and what makes it so dangerous, you're not alone.

If you're looking to invest in Bitcoin or other blockchain currencies, you could be at risk. Here's what everyone should know about this type of attack, as well as why it's such a huge threat to the blockchain world.

Before we start, we need to explain something about cryptocurrency mining and decentralized goods.

To fully understand what is a 51% attack, you need to understand how cryptocurrency mining tends to work. With cryptocurrency mining, people mine coins by approving transactions. As long as the majority of the transactions are mined quickly and honestly, the cryptocurrency will fare well.

To provide the proof of work necessary for a transaction. The computing power of blockchain mining is called the hash rate. As long as the hash rate is controlled by a wide variety of people, there shouldn't be any problems. The blockchain transactions happen smoothly and everyone (for the most part) acts on good faith.

As long as the majority of users are acting in good faith and doing transactions properly, everything works out well. That's what makes 51% attacks so vicious.

So, what is a 51% attack, anyway?

A 51% attack is a cyberattack where a small group of people slowly take over the majority of a cryptocurrency's hash rate. If 51% or more of all transactions have to go through a small group of people, the people who end up controlling the hash rate end up controlling the cryptocurrency.

What is a 51% attack good for?

A 51% attack is great for destroying an entire blockchain economy, if it's actually able to be done. Controlling a currency's transaction on that level could easily cripple users' ability to get anything done—and in turn, could actually cause the cryptocurrency in question to slowly die.

Due to the fact that hackers could only really control the past couple of blocks, older and more established cryptocurrencies like Bitcoin would be very difficult to do. Just because a 51% attack was launched doesn't mean it can be successful.

What is a 51% attack capable of doing?

A 51% attack can allow hackers to potentially influence or rewrite blocks in the blockchain. In theory, a successfully executed 51% attack would allow them to halt mining operations, reverse successfully executed transactions, or even cause double-spending and counterfeiting to occur.

So far, there have only been a handful of moments where a 51% attack has been documented. Ghash.io, Krypton, and Shift have all been victims of 51% attacks or have been involved in them. Since there have only been a few 51% attacks, most people tend to think of it as a mostly-theoretical occurrence.

Those who stay abreast of blockchain news using apps like ChainHub, though, will tell you that there's nothing theoretical about these attacks.

Now that we know what 51% attack is used for, we can figure out what it'd do to Bitcoin.

Bitcoin was one of the first (if not the first) cryptocurrencies to ever exist, and while that may be excellent for value, that doesn't always mean good things for innovation and security. Because its code is so well-known, it would probably be very deeply affected by a 51% attack.

In fact, if it was possible to get 51% of Bitcoin's hash rate, it would very likely wreak havoc on the blockchain economy—not to mention any financial institutions that have invested in this tech.

Because so many different Bitcoin mining groups exist, a 51% attack would be very difficult to do on Bitcoin.

Now that you know what a 51% attack is all about, you need to realize how hard it can be to actually make it happen. Even the best black hat hackers in the world have a hard time pulling this kind of cyber attack on a blockchain economy as big as Bitcoin.

Think about how many users would end up having to be a part of that group in order for the 51% attack to launch, and you'll see why a lot of people are very skeptical that an attack like this could end up being successful.

It'd take a lot of coding and a lot of manpower. So, if you're looking to know what is a 51% attack on the Bitcoin network, the answer is "mostly theoretical."

To a point, Bitcoin's massive economy and long blockchain ledger history make it as impressive as it is.

To this date, no one has been able to take control of over 51% of the Bitcoin network. Additionally, more Bitcoin transactions happen every day, and more miners are being added into the mix every minute.

Because hackers can only reverse-change the past couple of blocks, damage would also be minimized due to the exceptionally long chains that Bitcoin typically has.

Is a 51% attack on Bitcoin even possible?

Though it's true that blockchain has been changing the face of cybersecurity, one should never assume that it's totally hackproof. As hackers have repeatedly shown us, anything is possible with the right brains behind the job.

The way things usually hit with these attacks, hindsight often is what ends up making news headlines. It's amazing to think that one day, people might not ask if it's possible—but rather, why no one knew what is a 51% attack capable of until it actually hit Bitcoin.

So, what is a 51% attack on Bitcoin?

A theoretical outcome of a lot of hackers working together—as of right now. In the future, a 51% absolutely could happen.