Definition: NTLMSSP (NT LAN Manager Security Support Provider) is a security protocol used in Windows environments for authentication, integrity, and confidentiality. It is part of the NTLM (NT LAN Manager) protocol suite.

Function: Provides a challenge-response mechanism for authenticating users and securing communications within a network.

Components:

 * '''Client''': The system requesting authentication.
 * '''Server''': The system validating the authentication request.
 * '''Domain Controller''': In a domain environment, the server that verifies user credentials.
 * '''NTLM Messages''': Series of messages exchanged between the client and server to perform authentication.

Features:

 * '''Challenge-Response Authentication''': Ensures that passwords are not sent over the network in plaintext.
 * '''Session Security''': Provides options for message integrity and confidentiality.
 * '''Backward Compatibility''': Compatible with older Windows systems and applications that do not support newer protocols like Kerberos.

Usage: Commonly used in environments where Kerberos is not available or practical, such as standalone systems or during fallback scenarios.

NTLM Authentication Process:

 1. **Negotiate Message**: The client sends a negotiate message to the server, indicating its supported NTLM options.
 2. **Challenge Message**: The server responds with a challenge message containing a random challenge.
 3. **Authenticate Message**: The client responds with an authenticate message containing the user's response to the challenge, encrypted with a hash of the user's password.
 4. **Verification**: The server verifies the response with the domain controller and either grants or denies access based on the result.

Configuring NTLM in a Windows environment:

 * Access the Group Policy Editor (`gpedit.msc`).
 * Navigate to `Computer Configuration` > `Windows Settings` > `Security Settings` > `Local Policies` > `Security Options`.
 * Configure the `Network security: LAN Manager authentication level` policy to use NTLMv2 response only.

Enabling NTLM auditing:

 * Use the Event Viewer to monitor NTLM authentication events by navigating to `Applications and Services Logs` > `Microsoft` > `Windows` > `NTLM`.

NTLMSSP: A security protocol used for authenticating users and securing communications within a Windows network, employing a challenge-response mechanism and providing backward compatibility with older systems and applications.