Version 4.1 - 5.1.h Identity-based services
There is actually a section of the documentation that covers Configuring the Identity Firewall.
"The Identity Firewall integrates with Microsoft Active Directory in conjunction with an external Active Directory (AD) Agent that provides the actual identity mapping. The ASA uses Windows Active Directory as the source to retrieve the current user identity information for specific IP addresses and allows transparent authentication for Active Directory users."
If there is something on this, I would expect it to be :
The key benefits of the Identity Firewall include:
•Decoupling network topology from security policies
•Simplifying the creation of security policies
•Providing the ability to easily identify user activities on network resources
•Simplify user activity monitoring
Again, most of the emphasis on Identity Services would likely be oriented towards the use of ISE instead of an AD Agent and the ASA. Instead of milking this section, I'm moving on.