Cryptocurrency system experiences multimillion-dollar theft

IEEE Spectrum : The systems for managing cryptocurrencies such as Bitcoin are intended to be secure. But as with all software systems, there are flaws that some users attempt to exploit. On 17 June a public investment system called the DAO, which is built around the Ether currency, was exploited in a way that allowed the attacker to steal more than 3 million Ether (at the time equivalent to about $60 million). Participants in the DAO use Ether to purchase DAO tokens, which give them proportional ownership of the DAO and a proportional vote in the group’s investments. The DAO is designed so that token holders can split off their shares and invest them for 27 days before returning the currency to the collective pot. The attacker managed to split away more than his or her original share of the collective investment. The person behind the attack now controls a split DAO that contains 100 times as many tokens as initially invested. Those surplus tokens were taken away from other investors. The developers behind the DAO are looking for a solution. Other than resetting the system to a point before the attack began, which is counter to the principles of block-chain currencies, there does not appear to be a way to restore the stolen funds to the original owners.