A replica of bitcoin-Vertcoin, launched to prevent miners from forming pools and gaining a monopoly on its network, has been compromised.

Mark Nesbitt, an expert on security issues, said that the Vertcoin blockchain, decentralizovanno, cryptanalytic algorithm PoW, came under Attack 51. A Coinbase engineer found that some anonymous cybercriminals had rented a large number of ASICs to attack a four-year-old cryptocurrency network. As a result, they received more than 50% of the hash power, which allowed them to own and manage the public blockchain Vertcoin.
The integrity of the pow cryptocurrency depends on the distributed nature of its network. It is considered decentralized when no mining pool has more than 50% of the network hash power. If a mining object takes control of most of the hash power, it can create individual blocks from any arbitrary previous block, creating two versions of the same blockchain. And if an alternative blockchain controlled by one object starts generating more blocks than the rest of the network, it can lead to a situation called network reorganization.
If a large number of coins are in the hands of a malicious miner, he can also launch a double-spending attack on the network. For example, a miner can initiate a transaction on the main blockchain and replicate the same transaction on an alternative fake blockchain. As a result, both transactions send the same coin, and only one of them can be confirmed and the other remains invalid. Nesbitt explained:
In 4 different incidents, the latest of which is currently ongoing, Vertcoin (VTC) has gone through 22 deep network reorganizations, 15 of which included double VTC spending. We believe these attacks may have resulted in the theft of more than $ 100,000. The biggest reorganization was more than 300 blocks in depth.
Altcoins vulnerability
Nesbitt, speaking about the incident with Vertcoin, also warned about other problems of PoW-altcoins in the form of potential losses, accusing them of the lack of effective countermeasures:
This is due to the fact that exchanges allow you to quickly transfer deposits to different assets and then withdraw. An attacker can make a Deposit, exchange funds for another asset, transfer a new asset from the platform, and then cancel the network transactions used for the initial Deposit by recovering the funds.
Nesbitt cited similar incidents that occurred in the industry this year, naming BTG, XVG, and MONA. In the end, all of them were excluded from the largest global platforms for cryptocurrency trading. "I urge you to patronize exchanges that ensure the safety of customer funds as their highest priority," Nesbitt concluded.
Link to the source of information (Russian) -
https://altstake.io/news/vertcoin-podvergsya-atake-51-poteri-ughe-prevysili-100000