Over 300 blocks were reversed in the course of the 51% attack.
The anonymous Firo crypt coin, formerly known as Zcoin, is the last working test coin to suffer a 51% attack.
When tweeting on Wednesday, Firo revealed that the protocol had suffered a 51% attack and advised holders to stop all transactions until the network returned to normal.
Ethereum Classic suffers another 51% attack
The attack would have come to light when users reported that previously confirmed transactions had not been confirmed. This was apparently the result of a blockchain reorganisation attack initiated by the attacker.
According to Binance’s CEO, Changpeng Zhao, the blockchain reorganisation resulted in a reversal of 306 blocks. Details of the attack shared by team members in the project’s Telegram group showed the confirmed „orphan“ transactions attacked the previous day.
As we go to press, Firo’s team says the attack has stopped. Commenting on the economic cost of the attack, Firo’s project manager, Reuben Yap, told Cointelegraph
„The exchanges are the ones that are losing out, as the attacker had deposited funds that have now been reversed due to the 51% attack. We are still working with the exchanges to resolve the issue. As far as we know at the moment, both Binance and Indodax were affected“.
The 51% attack affects over $5 million of Ethereum Classic
Firo said the attack was not due to a coding error. „We often evaluate to see what kind of hash rate is easily profitable in MTP and it never came close to something that could have carried out an attack on this scale,“ said Yap.
For Firo’s team, the attack was only possible because the project had not yet implemented chainlocks on the main network. A Chainlock is a secondary validation layer that supposedly mitigates a 51% attack.
According to Yap, with Chainlocks enabled, an attacker would need to control at least half of all of Firo’s master nodes in addition to the usual 51% mining hash rate domain.
Firo would have completed the test protocols for Chainlocks Bitcoin News Trader and is ready for full implementation in the coming weeks. When integrated, Chainlocks will be the last protocol feature added to the project after activating the Lelantus update.
The Grin network suffered a 51% attack, and the GRIN token is still resilient
The timing of the attack was suspicious, according to Yap, who said Firo is investigating possible motives. „To make a double expenditure of this magnitude, the attacker had also acquired significant amounts of Firo legitimately,“ he said, adding:
„The timing of the attack is also strange given that MTP has been active in our network for a long time and it has been several months since the first halving. Attacking us when we are so close to deploying chain locks seems strange“.
On the price side, Firo (FIRO) has dropped almost 12% in the last 24 hours. This decline has interrupted a positive 14-day trading period for FIRO, but the privacy currency is still above 73% since the beginning of 2021.
Work trial block chains with significantly lower hash rates have been attacked at 51% on several occasions. In 2020, Ethereum Classic suffered multiple 51% attacks and one such incident resulted in the loss of approximately USD 5.6 million in FTE. Grin, another privacy-focused kryptonie, also suffered a 51% attack in 2020.