Error handling refers to how applications manage unexpected conditions, such as invalid input, unavailable services, or system failures. Secure error handling is about striking a balance: errors must be reported clearly enough for troubleshooting, but not so detailed that they reveal internal system logic to attackers.
For instance, returning “invalid username or password” provides more information to attackers than a generic “authentication failed.” Likewise, stack traces or SQL error messages should not be exposed to end users, as they can guide attackers in crafting injection payloads. Proper error handling improves resilience by preventing system crashes while avoiding information leakage that could be weaponized.