The balances mapping is now declared as private to prevent direct external access. Access to balances is controlled through the getBalance function.

The onlyOwner modifier is applied to critical functions like freezeAccount and unfreezeAccount, ensuring that only the contract owner can freeze or unfreeze accounts.

A frozenAccount mapping is introduced to prevent frozen accounts from performing withdrawals. A notFrozen modifier is created to check if the sender's account is frozen before allowing withdrawals.

Deposit and Withdrawal events are emitted whenever funds are deposited or withdrawn, allowing external systems to monitor contract activity.

Additional validation checks are added to ensure that deposit amounts are greater than zero and that withdrawal amounts do not exceed the account balance.