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# Vertcoin (VTC) was 51% attacked
Vertcoin is a Bitcoin clone that aims to be ASIC-resistant by hard forking to new mining algorithms whenever ASICs are deployed on the network. [Vertcoin was previously 51% attacked in Dec 2018](https://medium.com/coinmonks/vertcoin-vtc-is-currently-being-51-attacked-53ab633c08a4) and has since changed its proof-of-work algorithm to Lyra2REv3. On Nov 30th 2019, a Vertcoin miner noticed a large upswing in hashrate rental prices for Lyra2REv3 on Nicehash. This was combined with workers connected to Nicehash's stratum server being sent work for unknown (non-public) Vertcoin blocks. I contacted Bittrex, Vertcoin's most prominent exchange, to recommend they disable the Vertcoin wallet on their platform once it became clear an attack was in progress, which they subsequently did.
## The Attack
On [Sunday, 1 December 2019 15:19:47 GMT](http://hubris.media.mit.edu:5000/reorgs/65625) 603 blocks were removed from the VTC main chain and replaced by 553 attacker blocks. We note that 600 blocks is the current confirmation requirement for VTC on Bittrex. There were [5 double-spent outputs](http://hubris.media.mit.edu:5000/doublespends/VTC?reorg=65625) in which ~ 125 VTC (~$29) was redirected. Each of the double-spent outputs are coinbase outputs owned by the attacker and it is unknown to whom the coins were originally sent before being swept to an attacker address after the reorg.