On many Proof-of-Stake networks, there exists a mechanism known as “slashing”. Slashing is any process by which some portion of stake delegated to a validator is destroyed as a punitive measure for malicious actions undertaken by the validator.
This mechanism incentivizes validators not to undertake such actions, as less stake delegated to a validator means that validator then accrues fewer rewards. Being slashed can also be seen as a reputational risk for retaining current or attracting potential future stake.
Slashing also poses a risk to token holders who could potentially lose some of their tokens if they have delegated to a validator which gets slashed. The presence of slashing could incentivize token holders to only delegate their tokens to validators they feel are reputable, and not to delegate all their tokens to a single or small number of validators.
On Solana, slashing is not automatic. If an attacker causes the network to halt, they can be slashed upon network restart. For more information, please check out the Solana docs.