Which layer is NOT part of the vault security for stored credentials?

The Application Layer Gateway does not form part of the vault security for stored credentials in the context of CyberArk's architecture. Vault security primarily focuses on controlling access and ensuring the protection of sensitive credential data through mechanisms such as Mandatory Access Control, which dictates who can access what within the system, and through the use of firewalls that monitor and control incoming and outgoing network traffic based on security rules.

Audit logging is also integral to vault security, as it provides a means of tracking and recording access and changes to stored credentials, thereby enhancing accountability and compliance.

In contrast, while an Application Layer Gateway enhances security by acting as a mediator for application-level traffic, it doesn't directly contribute to the vault's internal mechanisms for securing stored credentials. Its primary function is more related to handling requests and responses between clients and servers, rather than enforcing security measures on the vault’s stored data.