Network Level Authentication RDP is one of the Remote Desktop Protocol (RDP) security measures that protect remote desktop sessions against unauthorized access. Network Level Authentication (NLA) authenticates before a remote session is set up, thus minimizing the attack surface and overall security. As the threat to RDP vulnerabilities remains on the increase, NLA is an essential countermeasure against brute-force attack, unauthorized logins, and man-in-the-middle attacks.
This article presents an overview of Network Level Authentication RDP, its benefits, how it works, steps for configuration, troubleshooting, and security best practices.
What is Network Level Authentication (NLA)?
Network Level Authentication RDP is an authentication choice that forces the user to authenticate prior to accessing a remote desktop. NLA appeared first in Windows Vista and Windows Server 2008 and can be used to improve security by granting only authenticated users to create an RDP connection.
Previously, the RDP sessions were initiated anonymously, and therefore the hackers could take advantage of the loopholes even prior to the credential authentication. Network Level Authentication RDP closes such loopholes by enforcing network level authentication and thereby minimizing the unauthorized access along with minimizing other security loopholes.
How Network Level Authentication Works
NLA is synchronized with Credential Security Support Provider (CredSSP) to authenticate the user prior to opening an RDP session. These procedures are as follows:
- Client Authentication: When a user tries to connect using RDP, client computer authenticates the user initially using CredSSP.
- Credential Verification: Credentials entered by the client are checked with security configurations on the server.
- Secure RDP Session Creation: The remote desktop session is established following successful authentication, lowering the server from brute-force attacks on illegitimate access.
- Session Encryption: The link is encrypted through TLS or other sound encryption techniques in order to uphold data integrity as well as confidentiality.
Through preceding authentication to session creation, NLA mitigates brute-force attacks and unauthorized entry to the RDP server.
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Advantages of Having NLA for RDP
1. Improved Security
- Blocks unapproved access by authenticating before starting the session.
- Minimizes the attack surface for brute-force attacks on RDP login screens.
- Blocks any prospective man-in-the-middle attacks by encrypting credential transmission.
2. Decreased Attack Surface
- Because authentication is done before the RDP session is opened, it minimizes exposure to unapproved users.
- Blocks malware and ransomware that take advantage of open RDP sessions.
3. Decreased Resource Consumption
- Authentication is done before launching the graphical user interface, lessening unnecessary resource consumption.
- Prevents authenticating unauthenticated connection requests, thereby enhancing performance.
4. Integration with Active Directory and Group Policy
- Facilitates centralized management of authentication.
- Permits enforcement of security policy on the machine and users.
Enabling Network Level Authentication in Windows
Step 1: Determine if NLA is Supported on Your Computer
NLA needs:
- Windows Vista/Windows Server 2008 or later.
- NLA-capable RDP client (Remote Desktop Connection 6.0 or later).
- Remote server must have been configured for NLA connections.
Step 2: Enable NLA for Remote Desktop Host
- Open System Properties of the remote computer.
- Click Remote.
- In Remote Desktop, click Allow connections only from computers running Remote Desktop with Network Level Authentication.
- Click OK and Apply.
Step 3: Group Policy settings for NLA
- Open Group Policy Editor (gpedit.msc).
Navigate to:
- Computer Configuration → Administrative Templates → Windows Components → Remote Desktop Services → Remote Desktop Session Host → Security.
- Enable Remote connections to ask users to authenticate themselves using Network Level Authentication.
- Apply policy and restart computer.
Step 4: NLA Setup using Windows Registry (Experts only)
- Open Registry Editor (regedit).
Go to:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Terminal Server\WinStations\RDP-Tcp- Search for User Authentication and set its value as 1 (enables NLA).
- Restart the computer.
Resolving General NLA Issues
1. Can’t connect when NLA is enabled
- Verify that the RDP client is NLA-enabled.
- Verify that the user has the appropriate permissions to access the remote server.
- Verify that the remote computer is joined to an Active Directory domain (if necessary).
2. “An Authentication Error Has Occurred” Message
- Verify the remote computer is up to date for security patches.
- Temporarily disable NLA to verify if the problem is with authentication policies.
3. CredSSP Encryption Oracle Remediation Error
- Update the local RDP client to the latest version.
Edit the Group Policy setting:
- Go to Computer Configuration → Administrative Templates → System → Credentials Delegation.
- Turn on Encryption Oracle Remediation and configure to apply to Mitigated.
- Adding Multi-Factor Authentication to Enhance RDP Security
While NLA authentication RDP provides secure security, RDP multi-factor authentication (MFA) should be turned on for additional security boost. RDP two-factor authentication (2FA) requires users to provide another authentication factor, e.g., mobile OTP or biometrics, reducing the chance of credential compromise.
To set up RDP network level authentication with MFA usage:
- Use an authentication provider like Microsoft Azure MFA or Duo Security.
- Set RDP Gateway to ask for multi-factor authentication.
- Expand MFA policy with Active Directory for the centralized management of authentication.
Conclusion
Network Level Authentication RDP is one of the primary security features of RDP, adding security through authenticating prior to actually setting up a remote session. Through reducing the attack surface, brute-force attack blocking, and enforcing an authenticated and secure process, NLA drastically improves remote access security.
NLA and other security best practices like RDP multi-factor authentication, hard passwords, and network constraint can sufficiently secure RDP sessions from cyber attack. Since RDP is also an attacker’s choice of target, organizations and end users must implement countermeasures in securing remote desktop access by enforcing Network Level Authentication RDP and security best practice.
FAQs
1. What is Network Level Authentication (NLA) for RDP? Network Level?
Authentication (NLA) is an RDP security feature that prompts users to authenticate prior to a remote session establishment. It guards against unauthorized use by only allowing authenticated users to connect to the remote server.
2. How does NLA enhance RDP security?
NLA improves security by minimizing the attack surface of RDP connections. It makes sure that authentication occurs prior to establishing the remote desktop session, stopping brute-force attacks, unauthorized login attempts, and server resource utilization.
3. How do I turn on Network Level Authentication (NLA) in Windows?
To turn on NLA:
Open System Properties (sysdm.cpl).
Navigate to the Remote tab.
Under Remote Desktop, choose Allow connections only from computers running Remote Desktop with Network Level Authentication.
Click Apply and OK.
4. What are the system requirements for NLA?
NLA needs:
Windows Vista/Windows Server 2008 or more recent.
An NLA-enabled Remote Desktop client (RDP 6.0 or higher).
The remote server must have NLA connections accepted.
