It is not always easy to determine which server technologies apply to the applications for which you are creating security policies. Server technologies can be server-side applications, frameworks, programs, web servers, operating systems, and so on, and they are associated with one or more sets of attack signatures that can be added to the policy. This allows you to assign a more selective set of attack signatures to the policy, that is, signatures that specifically apply to the technologies used in the application being protected.
When you first create a security policy, you have the opportunity to select server technologies that you know about. Once the policy is created, you can have it automatically detect server technologies. In this case, the policy can detect appropriate server technologies, and can continue to detect new server technologies if the back-end server infrastructure changes, if new systems are added, or if an attack signature update adds a new server technology that is appropriate for the policy.
The system can automatically detect the server technology on Request headers and payloads only when a successful response code is received (1xx/2xx/3xx). For Responses, server technology can be detected only if "Content-Type" header is in the response. The system also learns technologies from error responses, such as 4xx and 5xx status codes (even if they are not listed in the HTTP Response Status Codes used to learn traffic in the Learning and Blocking Settings).
You can also manually add server technologies to the policy if you determine that certain ones are appropriate for the applications being protected and want to apply them right away.
When server technologies are included in the policy, the system creates a user-defined signature set for each server technology. If the technology has related or implied server technologies, they are added as well. The signature sets are added to the security policy with the Learn, Alarm, Block flags set, and new signatures are put into staging. The system learns server technologies from responses regardless of the Learn from response flag setting in the Learning and Blocking Settings .
If you later delete server technologies and want to delete the associated user-defined signature sets, you can go toand delete the sets there. Deleting the user-defined signature sets alone, however, does not remove the server technology from the list.