Privacy-focused digital currency, Firo, formerly known as Zcoin, suffered a 51% attack in the early hours of 20 January. Taking to Twitter, the team behind Firo notified traders about the attack and asked users not to make transactions until the network returned to a normal state.
XZC(FIRO) 51% attack, 306 blocks rolled back, to 2021-01-18 17:24:20(UTC). Another messy situations.
— CZ ? Binance (@cz_binance) January 20, 2021
Firo team further added:
We will post updates when we have them. Note this is not a coding error but a nature of PoW.
The Firo project is a Proof-of-Work (PoW) blockchain, and such projects tend to be prone to 51% reorgs, especially when a small to medium scale protocol is involved.
Previously, PoW blockchains such as Ethereum Classic, were attacked which resulted in the reorganization of over 7,000 blocks that corresponded to about two days of mining. Other PoW chains such as BCHA and Grin – which is also a privacy coin – suffered 51% attacks as well.
Exchanges are the ones at a loss as the attacker had deposited funds which have now been reversed because of the 51% attack…From what we know at the moment both Binance and Indodax were affected.
Firo is reportedly probing into the motives behind the attack as they are suspicious about the timing of the incident, which took place when they were close to deploying chainlocks. According to the Firo team, a feature on the blockchain called Chainlocks that mitigates such attacks was being tested on Firo’s testnet and was apparently “weeks away from deployment.”