2.3.11.13 (L1) Ensure 'Network security: Restrict NTLM: Outgoing NTLM traffic to remote servers' is set to 'Audit all' or higher

Information

This policy setting allows the auditing of outgoing NTLM traffic. Events for this setting are recorded in the operational event log (e.g. Applications and Services Log\Microsoft\Windows\NTLM).

The recommended state for this setting is: Audit all Configuring this setting to Deny All also conforms to the benchmark.

Note: Configuring this setting to Deny All is more secure, however it could have a negative impact on applications that still require NTLM. Test carefully before implementing the Deny All value.

Auditing and monitoring NTLM traffic can assist in identifying systems using this outdated authentication protocol, so they can be remediated to using a more secure protocol, such as Kerberos. The log information gathered can also assist in forensic investigations after a malicious attack.

NTLM and NTLMv2 authentication is vulnerable to various attacks, including SMB relay, man-in-the-middle, and brute force attacks. Reducing and eliminating NTLM authentication in an environment reduces the risk of an attacker gaining access to systems on the network.

Solution

To establish the recommended configuration via GP, set the following UI path to Audit all or higher:

Computer Configuration\Policies\Windows Settings\Security Settings\Local Policies\Security Options\Restrict NTLM: Outgoing NTLM traffic to remote servers

Impact:

The event log will contain information on outgoing NTLM authentication traffic.

See Also

https://workbench.cisecurity.org/benchmarks/16913