Title

The system is not configured to meet the minimum requirement for session security for NTLM SSP based Clients. (Cat II impact)

Discussion

Microsoft 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”, ”Require 128-bit encryption”, ”Require Message Integrity”, and ”Require Message Confidentiality”, 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: 537395248 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”, ”Require Message Integrity”, and ”Require Message Confidentiality” (all options selected).

Additional Identifiers

Rule ID: SV-3382r1_rule

Vulnerability ID: V-3382

Group Title: Session Security for NTLM SSP Based Clients

Expert Comments

CCIs tied to check.

Controls tied to check. These are derived from the CCIs shown above.