There is a simple setup with IDM, which many customer admins like to implement in proof of concept projects, and later migrate directly into production. In this setup, IDM is deployed in DMZ and protected by some Load Balancer: F5 BigIP or Citrix NetScaler or KEMP ADC or whatever. Let's take F5 as an example:
The challenge here is to correctly configure the load balancing appliance, which some admins fail to do. The configuration often used is a simple "SSL Pass-through". What this leads to, is access of unauthenticated users to the API endpoints of IDM. IDM responds to these requests and reveals a lot of inside information, which may compromise security. Here are some examples of such links:
https://<IDM External URL>/SAAS/jersey/manager/api/
In the worst case scenario, the admin console will also be available externally (/SAAS/admin/* link).
To mitigate this, L7 URL filtering, whitelisting of external URLs must be configured on the load balancing appliance. A second option is to create two VIP interfaces on the load balancing appliance, and close all the vulnerable URLs for external access. Here is the example schema: