Application identification is a feature that enables SRX Series devices to identify and classify network traffic based on application signatures or custom rules. Application identification can enhance security, visibility, and control over network applications.
Two statements that are true about application identification are:
Application identification can identify nested applications that are within Layer 7: Nested applications are applications that run within another application protocol, such as HTTP or SSL. For example, Facebook or YouTube are nested applications within HTTP. Application identification can identify nested applications by inspecting the application payload and matching it against predefined or custom signatures.
Application signatures are not the same as IDP signatures: Application signatures are patterns of bytes or strings that uniquely identify an application protocol or a nested application. IDP signatures are patterns of bytes or strings that indicate an attack or an exploit against a vulnerability. Application signatures are used for application identification and classification, while IDP signatures are used for intrusion detection and prevention.
Reference: = [Application Identification Overview], [Application Identification Concepts], [Understanding Signature Rules and Protocol Anomaly Rules]