Secure Error Handling & Logging Flashcards

What should a production application show users when an unhandled exception occurs?

Answer: A generic error message, with details logged on the server only

Detailed errors leak information an attacker can use, such as stack traces, queries and versions. Users should get a generic message, while the details go to secure server-side logs.

What does the 'fail securely' (fail closed) principle mean?

Answer: When an error occurs, the system defaults to denying access

Failing securely means that if an exception happens, for example during an authorization check, the system ends up in a secure state and denies access rather than allowing it.

Which of these should NEVER be written to application logs?

Answer: Plaintext passwords and full session tokens

Logs are often widely accessible and kept for a long time. Passwords, session tokens, card numbers and similar secrets must never be logged, or should be masked.

An attacker submits input containing CR/LF characters so that fake entries appear in the log file. What is this attack called?

Answer: Log injection (log forging)

Log injection uses newline characters to forge log entries, which can mislead investigators. The defense is to sanitize or encode user data before it is logged.

Which coding practice weakens security in exception handling?

Answer: Using empty catch blocks that swallow exceptions

Empty catch blocks hide failures, can leave the application in an inconsistent or insecure state, and remove evidence of attacks.

Which events are most important for a security audit log to capture?

Answer: Authentication successes and failures, authorization failures and changes to sensitive data

Security logging should record authentication events, access-control failures, input validation failures and changes to sensitive data. Together these support detection, incident response and accountability.