The system will be configured to meet the minimum session security requirement for NTLM SSP based clients.

From Windows Server 2008 R2 Domain Controller Security Technical Implementation Guide

Part of Session Security for NTLM SSP Based Clients

Associated with: CCI-000366

SV-32341r1_rule The system will be configured to meet the minimum session security requirement for NTLM SSP based clients.

Vulnerability discussion

Windows has implemented a variety of security support providers for use with RPC sessions. In a homogenous Windows environment, all of the options should be enabled and testing should be performed in a heterogeneous environment to determine the maximum-security level that provides reliable functionality.

Check content

Analyze the system using the Security Configuration and Analysis snap-in. Expand the Security Configuration and Analysis tree view. Navigate to Local Policies -> Security Options. If the value for “Network security: Minimum session security for NTLM SSP based (including secure RPC) clients” is not set to “Require NTLMv2 session security” and “Require 128-bit encryption”, then this is a finding. The policy referenced configures the following registry value: Registry Hive: HKEY_LOCAL_MACHINE Registry Path: \System\CurrentControlSet\Control\Lsa\MSV1_0\ Value Name: NTLMMinClientSec Value Type: REG_DWORD Value: 0x20080000 (537395200) Warnings: Microsoft warns that setting these may prevent the client from communicating with legacy servers that do not support them. “Require NTLMv2 session security” will prevent authentication, if the “Network security: LAN Manager Authentication level” is set to permit NTLM or LM authentication. Documentable Explanation: If these settings need to be modified in a mixed Windows environment, the changes should be documented with the IAO.

Fix text

Configure the policy value for Computer Configuration -> Windows Settings -> Security Settings -> Local Policies -> Security Options -> “Network security: Minimum session security for NTLM SSP based (including secure RPC) clients” to “Require NTLMv2 session security”, ”Require 128-bit encryption” (all options selected).

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