In a nutshell: The DAO attack and how to steal $60 million worth of cryptocurrency

On Friday morning the Internet was abuzz with posts, messages and tweets that someone had stolen $60 million worth of a cryptocurrency called ether from an organisation called The DAO. While the average joe probably understands that a pretty big heist has taken place, any of the other terms are likely to make little sense. So, let’s deconstruct the headline and try to explain what happened as well as what the consequences of this might be.

The DAO is a so-called Decentralized Autonomous Organization (“DAO”). DAOs run through rules encoded as smart contracts, which in turn are computer programs that facilitate, verify, or enforce the negotiation or performance of a contract, or that make a contractual clause unnecessary. In simple terms, think of any contract between two parties that gets translated into code, so it doesn’t need any external action but does automatically what was agreed. Smart Contracts are a pretty revolutionary and powerful concept by itself and if you want to know more about it, read our separate post on the subject.

The idea of a DAO somewhat is that once launched it can run based on its underlying smart contracts alone. The DAO’s smart contracts are based on Etherum, a public blockchain (which is a distributed database – for more information on blockchain, see here) platform with programmable transaction functionality that is also the basis for ether (or ETH), a cryptocurrency. ETH is a cryptocurrency similar to Bitcoin, but very popular since it offers a wider range of services and therefore sometimes considered a considerable challenger of Bitcoin as the leading cryptocurrency.

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The DAO is fuelled using ether, which creates DAO tokens. DAO token holders will have the right to vote on investment proposals (proportional to the number of tokens held) as well as the opportunity to receive rewards generated by the output of the work from the contractors’ proposals. Since it is decentralized autonomous organization that is represented only by its smart contracts, it has no physical address and people only interact as contractors or curators, but not in managerial roles in the traditional sense. However, it is supported by a limited company and a cryptocurrency exchange in Switzerland, both chosen with a view to the legal and regulatory framework. The DAO is intended as a form of venture capital vehicle that would invest in projects in the sharing economy. Prior to the attack, the fund’s value was around $150 million in ether.

So while its creators hoped to build a more democratic financial institution that would be safe against the fallibility of humans by trusting the trustless concept of the blockchain and smart contracts, it seems human error is at the bottom of the heist.

Though it is not entirely certain yet how the money has been stolen, it appears that the hacker exploited a programing mistake in the code of the DAO. Weaknesses in the code had already been highlighted before and experts in the field had already called to fix critical problems. At this point it is important to recall that as a blockchain-enabled organization, the DAO is completely transparent and everything is done by the code, which anyone can see and audit. So, it seems that what happened – in a very simplified way – was that the hacker sent repeated transaction request to transfer funds to a DAO clone. Because of the programming error, the system possibly did not immediately update the balance, allowing the attacker to drain the account.

Since then the discussion has been how to respond to the attack. In an initial response, Vitalik Buterin, one of Ethereum’s founders, publicly asked online currency exchanges to suspend trading of ether and DAO tokens as well as deposits and withdrawals of the cryptocurrency.

Because of a restriction in the code pay-outs are delayed for at least one week, possibly even longer, the hacker will not be able to access the funds and give The DAO community some time. Several options are currently discussed: The community could decide to do nothing, preserve the system and let the DAO token holders loose their investment. Or the so-called “hard-fork” where the Ethereum community could decide to roll back all transactions to a specific point in time before the attack. Or the network could be updated to ensure that all transactions from the hacker’s ether address are blocked, basically freezing the account and trying to exploit a similar programing error to “steel” the money back since the DAO clone is likely to contain the same code structure that made the original attack possible.

Regardless which course is decided on, what are the likely consequences for the DAO, Ethereum and the Blockchain in general after this incident?

Stephen Tual, COO of, the company that had worked on the development of The DAO, stated that The DAO is definitely going to close. Whether that is the case is to be seen as in a leaderless organization no one person alone can decide on the fate of the organization. The future of the investment vehicle is cast into serious doubt in any case by the theft itself, as it is questionable whether anyone would put money in a construction that has a proven vulnerability even when its makers promise to fix the issues. Trust, after all, is relevant even for a trustless concept when it comes to money.

The more damaging aspect for the DAO, but also for Ethereum and potentially even the blockchain technology lies potentially in the actions to get the ether back. In comments across the web it has been compared with a bailout for banks that are too big to fail and that investors simply didn’t understand the risks of their investments. If the system is supposed to be flawless and save against tempering, isn’t meddling with it because of an, albeit very significant and expensive, programming error, undermining the whole idea? If people decide on whether transactions are to be reversed or not instead of the underlying smart contract, what is the worth of such an instrument if it’s only useful if anything goes according to plan?

Regardless what happens next it is an immensely important case as well from a legal and regulatory perspective: One tweet even hinted that a short bet on Ether was placed on one cryptocurrencies exchange shortly before the attack, which reminds us that traditional regulatory aspects like Market Abuse are more than relevant in the digital age. The tweet demanded an investigation though that raises the interesting questions about jurisdiction, governing legal frameworks and regulation, but that is only a side aspect to the story for now (though it would make sense from an economical perspective since the thief is unlikely to be able to access the Ether he stole and in that way could gain a monetary benefit from the heist).

In an interesting post at Coindesk, a US lawyer discussed the incident from a perspective of criminal law (Theft? Yes!), civil law (sue the hacker? Sure, seems everything can be sued) and tort law.

And even more interesting is the question whether the hacker only exploited a loophole in the code. In a message to the DAO and the Ethereum community, which is allegedly from the person responsible for the attack, the hacker described his action simply as using an intentional feature of the code and stated that any action to get the funds back, would amount to seizure of my legitimate and rightful ether, claimed legally through the terms of a smart contract, threatening trying to do so with legal action.

Everything is in flux: at the time of writing this, the DAO community is voting on whether to take action and, if so, in what form. Someone claiming to be an intermediary on behalf of the attackers has published a note, making it look like their holding the stolen ether ransom, and tweets on the subject get seemingly posted every second.

So to summarise, plenty of open questions, an uncertain future for the DAO, but maybe there is a silver lining that comes from this. Maybe this is only a costly episode on a steep learning curve, similar to other forms of innovation, and maybe this will lead to more care, diligence and scrutiny in future blockchain projects, which in the end might not be so bad after all.


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