The rule "Duo User Bypass Code Used" focuses on monitoring the use of bypass codes within the Duo authentication framework. Bypass codes are used as an alternative method of authentication, allowing users to bypass standard two-factor authentication processes. The rule triggers when a bypass code is utilized for authentication, indicating that a user may have circumvented normal login procedures, either intentionally or unintentionally. This behavior can present a potential security risk, thus it's important to verify the legitimacy of such actions. The rule includes several tests: one to confirm a successful bypass code usage event, another to validate a standard successful authentication event to ensure it does not trigger the rule, and a third to check for denied actions resulting from outdated credentials. The logs to be analyzed are sourced from the Duo authentication logs, requiring specific indicators such as the event type, authentication device, and user's actions. If a bypass code is detected, follow-up with the associated user is advised to confirm the authenticity of the usage. Overall, the detection intends to ensure that bypass codes are used responsibly and that unauthorized access is prevented.