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

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Information

This policy setting determines which behaviors are allowed by servers 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 all of the 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. That is, these options help protect against man-in-the-middle attacks.

Impact:

NTLM connections will fail if NTLMv2 protocol and strong encryption (128-bit) are not both negotiated. Server applications that are enforcing these settings will be unable to communicate with older servers that do not support them.

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) servers

Default Value:

On Windows Server 2008 (non-R2): No requirements.

On Windows Server 2008 R2 and newer: Require 128-bit encryption. (NTLM connections will fail if strong encryption (128-bit) is not negotiated.)

See Also

https://workbench.cisecurity.org/files/3902