NDES Security Best Practices

In today's digital landscape, securing your network infrastructure is paramount. The Network Device Enrollment Service (NDES) plays a critical role in issuing certificates for network and mobile devices, making its security essential. This post outlines best practices for safeguarding NDES, treating it as a Tier 0 system, using Privileged Access Workstations, employing Hardware Security Modules, and more. By implementing these strategies, you can enhance the security of your network devices and protect your organization from potential threats.

This post is based on https://techcommunity.microsoft.com/t5/core-infrastructure-and-security/ndes-security-best-practices/ba-p/2832619 which is a hefty read albeit hugely useful.

Here is an expanded summary of the key points for NDES security best practices which might make more sense:

Treat NDES as a Tier 0 system: NDES is crucial for security, so it must be protected with the highest level of security controls and isolation.

A Tier 0 system is a critical component in an organization's IT infrastructure, representing systems that, if compromised, could lead to the compromise of the entire enterprise. These systems typically include domain controllers, certificate authorities, and other key security and identity management systems. Due to their importance, Tier 0 systems require the highest level of security controls and isolation to protect against attacks that could have severe organizational impacts.

Use a Privileged Access Workstation (PAW): Administer NDES from a PAW to reduce the risk of credential theft and improve security.

A Privileged Access Workstation (PAW) is a dedicated, highly secure computing environment used exclusively for sensitive tasks, such as managing NDES. The use of a PAW helps to reduce the risk of credential theft and other security breaches by isolating administrative activities from standard user environments, which are more likely to be exposed to malware and phishing attacks. PAWs should be configured with strict security controls, including application whitelisting, restricted internet access, and robust authentication mechanisms, ensuring that only authorized personnel can perform administrative tasks on NDES. This approach significantly enhances the overall security posture of your NDES deployment.

System Hardening: Limit administrative access, apply security baselines, and ensure the system is fortified against attacks.

System hardening involves implementing stringent security measures to protect NDES against potential threats. Here are key steps:

1. Limit Administrative Access: Only allow essential personnel to access the system, reducing the risk of unauthorized changes and potential breaches.
2. Apply Security Baselines: Use predefined security settings and policies to ensure a consistent and robust security posture across the system.
3. Regular Updates and Patching: Keep the system up to date with the latest security patches and updates to defend against known vulnerabilities.
4. Network Segmentation: Isolate NDES from other parts of the network to limit the potential impact of a security breach.
5. Monitoring and Logging: Implement comprehensive monitoring and logging to detect and respond to suspicious activities promptly.
   

Hardware Security Modules (HSM): Use HSMs for secure key management to protect cryptographic keys.

Hardware Security Modules (HSM) are dedicated hardware devices designed to manage and protect cryptographic keys. Utilizing HSMs for NDES offers several benefits:

1. Enhanced Security: HSMs provide a physically secure environment for key storage, reducing the risk of key exposure.
2. Tamper Resistance: They are built to resist tampering, providing a robust defense against physical attacks.
3. Performance and Reliability: HSMs are optimized for cryptographic operations, ensuring high performance and reliability in key management.
4. Compliance: Using HSMs can help meet regulatory and compliance requirements for data protection and cryptographic security.

Incorporating HSMs into your NDES deployment ensures that cryptographic keys are securely managed and protected, enhancing the overall security of your network.

Avoid Virtualization on General Servers: Virtualizing NDES on general-purpose servers can expose it to additional risks.

Virtualizing NDES on general-purpose servers can expose it to additional risks and vulnerabilities. Here's why it's important to avoid this practice:

1. Dedicated Resources: NDES requires dedicated hardware resources to ensure optimal performance and security. Sharing resources with other virtual machines can lead to resource contention and performance degradation.
2. Isolation: Virtualizing NDES on a general-purpose server increases the attack surface, as other virtual machines on the same host might be compromised and used as a pivot point for attacks.
3. Security Controls: General-purpose servers might not have the stringent security controls required for a Tier 0 system like NDES. Dedicated hardware can be more effectively hardened and secured.
4. Compliance: Using dedicated hardware can help meet compliance and regulatory requirements that mandate strict isolation and security for critical systems.

By avoiding virtualization on general-purpose servers, you can better protect NDES from potential threats and ensure it operates securely and efficiently.

Reverse Proxies for External Access: Use reverse proxies to manage and secure external access to NDES, reducing exposure to threats.

Using reverse proxies is a key practice for enhancing the security of NDES when it needs to be accessed externally. Here are the benefits and considerations:

1. Traffic Filtering: Reverse proxies can inspect and filter incoming traffic, blocking malicious requests before they reach the NDES server.
2. Load Balancing: They distribute incoming traffic across multiple servers, ensuring optimal performance and reliability.
3. SSL Termination: Reverse proxies handle SSL encryption and decryption, offloading these tasks from the NDES server and enhancing security.
4. Anonymity and Protection: By acting as an intermediary, reverse proxies help obscure the NDES server’s IP address, adding a layer of security against direct attacks.

Implementing reverse proxies thus significantly reduces the exposure of NDES to external threats, enhancing its security and performance.

Separate Certification Authorities: Employ separate CAs for NDES operations to contain any potential compromise and limit impact.

Using separate Certification Authorities (CAs) for NDES operations is a crucial security practice. Here’s why:

1. Containment of Compromise: Isolating NDES-specific CAs ensures that a breach in one CA does not affect other CAs, limiting the impact of potential security incidents.
2. Operational Separation: Different CAs can be tailored to specific operational needs, enhancing the security and efficiency of certificate issuance.
3. Enhanced Security: By separating duties and reducing the attack surface, you strengthen the overall security posture of your certificate infrastructure.
4. Compliance: Helps meet regulatory and industry standards for secure key and certificate management.
   

Secure Certificate Templates: Protect certificate templates and enforce stringent verification processes to ensure the integrity of issued certificates.

Securing certificate templates is essential for maintaining the integrity and security of certificates issued by NDES. Here’s how:

1. Access Control: Restrict access to certificate templates, ensuring that only authorized personnel can create or modify them.
2. Template Security Settings: Enforce stringent security settings on templates to prevent unauthorized issuance and misuse of certificates.
3. Verification Mechanisms: Implement robust verification mechanisms to ensure that certificate requests are legitimate and comply with organizational policies.
4. Monitoring and Auditing: Regularly monitor and audit the use of certificate templates to detect and respond to any suspicious activities promptly.
   

Hope this makes more sense than sense than the original post https://techcommunity.microsoft.com/t5/core-infrastructure-and-security/ndes-security-best-practices/ba-p/2832619 although I do recommend following this in detail when you put these measures to practice.