this is the test of Ethereum Casper protocol (I guess)
Casper has implemented a process by which they can punish all malicious elements. This is how POS under Casper would work:
The validators stake a portion of their Ethers as stake.
After that, they will start validating the blocks. Meaning, when they discover a block which they think can be added to the chain, they will validate it by placing a bet on it.
If the block gets appended, then the validators will get a reward proportionate to their bets.
However, if a validator acts in a malicious manner and tries to do a “nothing at stake”, they will immediately be reprimanded, and all of their stake is going to get slashed. (Full article here:
https://blockgeeks.com/guides/ethereum-casper/)
