This value impacts applications, from the point of view of the server, that use the NTLM SSP or secure RPC and specifies session security requirements for communication between the client and server.
| Hex value | Check box | Meaning |
| 0x0 | None checked | None. No security is used for session security. |
| 0x10 | Require message integrity | Message integrity. If the value of either this entry or the NtlmMinClientSec entry is 0x10, then the connection will fail unless message integrity is negotiated. |
| 0x20 | Require message confidentiality | Message confidentiality. If the value of either this entry or the NtlmMinClientSec entry is 0x20, then the connection will fail unless message confidentiality is negotiated. |
| 0x80000 | Require NTLMv2 session security | NTLMv2 session security. If the value of either this entry or the NtlmMinClientSec entry is 0x80000, then the connection will fail unless NTLMv2 session security is negotiated. |
| 0x20000000 | Require 128-bit encryption | 128-bit encryption. If the value of either this entry or the NtlmMinClientSec entry is 0x20000000, then the connection will fail unless 128-bit encryption is negotiated |
As best I can tell, this setting will primarily impact secure RBC communications such as between Outlook and Exchange when authenticating via NTLM.
Unanswered questions: how do these settings affect SMB traffic or do they? Do these setting apply to all RPC traffic, only secure RPC traffic or just secure RPC traffic authenticated via NTLM instead of Keberos? How do these setting affect traffic sent via the Kerberos SSP? If they don’t, how do you set similar requirements for Kerberos SSP?
Underlying registry key and value
NtlmMinServerSec
HKLM\SYSTEM\CurrentControlSet\Control\Lsa\MSV1_0
| Data type | Range | Default value |
| REG_DWORD | 0x0 | 0x10 | 0x20 | 0x80000 | 0x20000000 | 0x0 |
Excellent sources for more information on NTLM: http://davenport.sourceforge.net/ntlm.html by Eric Glass and http://www.microsoft.com/technet/technetmag/issues/2006/08/SecurityWatch/
More resources