2.3.11.9 (L1) Ensure 'Network security: Minimum session security for NTLM SSP based (including secure RPC) clients' is set to 'Require NTLMv2 session security, Require 128-bit encryption'

Information

This policy setting determines which behaviors are allowed by clients for applications using the NTLM Security Support Provider (SSP). The SSP Interface (SSPI) is used by applications that need authentication services. The setting does not modify how the authentication sequence works but instead require certain behaviors in applications that use the SSPI.
The recommended state for this setting is: Require NTLMv2 session security, Require 128-bit encryption.
Note: These values are dependent on the Network security: LAN Manager Authentication Level (Rule 2.3.11.7) security setting value.

Rationale:
You can enable both options for this policy setting to help protect network traffic that uses the NTLM Security Support Provider (NTLM SSP) from being exposed or tampered with by an attacker who has gained access to the same network. In other words, these options help protect against man-in-the-middle attacks.

Solution

To establish the recommended configuration via GP, set the following UI path to Require NTLMv2 session security, Require 128-bit encryption:
Computer Configuration\Policies\Windows Settings\Security Settings\Local Policies\Security Options\Network security: Minimum session security for NTLM SSP based (including secure RPC) clients

Impact:
NTLM connections will fail if NTLMv2 protocol and strong encryption (128-bit) are not both negotiated. Client applications that are enforcing these settings will be unable to communicate with older servers that do not support them. This setting could impact Windows Clustering when applied to servers running Windows Server 2003, see Microsoft Knowledge Base article 890761: You receive an 'Error 0x8007042b' error message when you add or join a node to a cluster if you use NTLM version 2 in Windows Server 2003 for more information on possible issues and how to resolve them.

Default Value:
Require 128-bit encryption. (NTLM connections will fail if strong encryption (128-bit) is not negotiated.)

References:
1. CCE-35447-2

See Also

https://workbench.cisecurity.org/benchmarks/14249

Item Details

Category: CONFIGURATION MANAGEMENT

References: 800-53|CM-6, CSCv6|13, CSCv7|5.1

Plugin: Windows

Control ID: 49d8dc4dc6c0f856ab665a41583777d99731da66ccffedad24659ec67478d6ca