Advanced policy expressions: evaluating text
You can configure a policy with an advanced policy expression that evaluates text in a request or response. Advanced policy text expressions can range from simple expressions that perform string matching in HTTP headers to complex expressions that encode and decode text. You can configure text expressions to be case sensitive or case insensitive and to use or ignore spaces. You can also configure complex text expressions by combining text expressions with Boolean operators
You can use expression prefixes and operators for evaluating HTTP requests, HTTP responses, and VPN and Clientless VPN data. However, text expression prefixes are not restricted to evaluating these elements of your traffic.