On Wednesday, June 3, a new version of Bitcoin Core 0.20.0 was released, which received experimental features to protect against large-scale attacks that could divide the Bitcoin network.
The new configuration that protects the Bitcoin peer-to-peer network is called Asmap. It maps existing node connections to Autonomous systems (AS) – Internet operators that connect multiple networks and define routing plans. After mapping, the configuration limits the number of connections to a single AS. Thus, hackers will not be able to isolate the Bitcoin node.
Note that in practice, such attacks have not yet been carried out – they require resources that only States have. The Erebus attack is that attackers use AS to cut off Bitcoin nodes from the rest of the network. In this way, you can isolate, for example, a large mining pool or cryptocurrency exchange.
After starting, a Bitcoin network node usually initiates eight connections with other nodes. And if the AS can act as a partner in all eight connections, the victim node will execute all the commands that the attackers pass to it. To do this, the AS needs to map the network, find the node addresses, and start accepting incoming connections. Over time, all connections of the node will go to the AS and it will be isolated from the main network.
The danger of an Erebus attack is also that it is almost invisible. All nodes are operating as usual, and there is no indication that the node has been isolated from the main network. Chain code Labs analyst and Bitcoin Core developer Gleb Naumenko stressed that not only Bitcoin, but most other cryptocurrencies are subject to Erebus attacks. This includes DASH, Litecoin, and Zcash.
Recall that in mid-April, Bitcoin developers Bryan Bishop (Bryan Bishop) I proposed a prototype of an in-network BTC storage that will help protect bitcoins from theft and ill-considered spending.