system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: If banks currently make transactions digitally, what prevents hackers from creating counterfeit digital currency? In other words how are banks kept accountable for the amount of money they actually have?
gpt
Banks *owe* the amount of money that's in each account — the depositors are free to withdraw it. So they have every incentive to prevent someone fraudulently raising the balance.

In addition to normal computer security they use *audit trails* — complete records of every deposit and where it came from — so that you can't just raise a balance without having a deposit.