It is much more complicated. First, Cardano use in-house built pull based network layer, so the attacker cannot exhaust your node even cannot do some resource attack against it, and even if some attacker is connected to your node and do some nasty stuff that causes protocol violation, it is just simply discomnected and dropped out of the 1000 cold list of other nodes in the aueue, and needs to wait a lot of time to rebuild its reputation. Anyway, it is very complex with a lot of mitigations of these kind of attacks. Secondly, you need money lot of money and bribe almost 500 pools (assuming nash) to be successfully alter the chain, it is like bribe 500 bitcoin miner pool from a theoretical 1000 evenly distributed hashpowers bitcoin miners/pools.