What is Network Access Control? A Complete Guide to NAC

Network access control (NAC) is a critical component of any organization’s cybersecurity strategy. As companies adopt increasingly flexible work environments and emerging technologies like the Internet of Things (IoT), their networks have expanded rapidly. More users, devices, and access points mean more potential vulnerabilities that attackers could exploit.

Implementing NAC solutions lets organizations stay securely connected despite relying on a complex, dynamic infrastructure.

Read on to learn everything you need to know about NAC from the network access control definition and capabilities to use cases, implementation steps, and key considerations around choosing a vendor.

What is network access control?

Network access control refers to the systems and policies designed to govern access to an organization’s network-connected resources. This includes both physical devices like PCs and routers, as well as virtualized and cloud-based assets.

NAC solutions focus on enforcing security protocols around who and what can connect to networked systems. They authenticate user identities and ensure devices meet compliance standards before granting admission. Once admitted, users may face additional permissions, restrictions, and monitoring based on their access tier.

Overall, the primary capabilities of NAC include:

• User and device access management
• Network security policy enforcement
• Endpoint compliance validation
• Threat monitoring and incident response
• Flexible, role-based access control

In other words, the short answer to the question, “What is NAC?” is that it’s a solution that authenticates users, authorizes device access, enforces security policies, and monitors network activity to keep a company’s network safe. 

Types of network access control

There are two primary categories of network access control (NAC) solutions that organizations leverage to govern access within their environments:

Pre-admission NAC 

Pre-admission NAC solutions focus on evaluating any attempts by a user or device to gain initial access to the network. Upon receiving an access request at the network perimeter, pre-admission NAC tools check the supplied credentials against user directories and access control lists. 

They also confirm the requesting endpoint meets security standards through policy checks before determining whether to allow or deny network admission.

Pre-admission NAC acts as the first line of defense to verify identities and device compliance while blocking unauthorized users. IT teams can customize authentication requirements within pre-admission NAC policies as needed. 

For example, multi-factor authentication could be mandated for all external connections. Any user that fails to present a valid tokenized secondary credential would be automatically rejected.

Post-admission NAC

Post-admission NAC refers to controls and monitoring applied to users after they have logged in to the network. In some cases, post-admission NAC may integrate with pre-admission tools to share access details. However, post-admission NAC is primarily concerned with enforcing on-going restrictions around what authenticated endpoints can access within the network.

Common post-admission NAC capabilities include segmenting the network into zones isolated by internal firewalls, continuously tracking user activity, restricting lateral movements between areas, and automatically disabling suspicious connections. 

These controls limit what damage a potential intruder could inflict by containing unauthorized access attempts. If malware penetrated a user’s device, post-admission NAC would observe the resulting abnormal outbound activity to the rest of the network and block it immediately.

How does network access control work?

NAC solutions rely on pre-defined security policies and advanced capabilities to govern each network access attempt.

Endpoint detection

The first step is identifying any device trying to connect to the network entry point, whether that be over a VPN, wired office connection, Wi-Fi, or another method. NAC tools immediately detect and log connection requests.

User and device authentication

Many NAC systems then validate the user and device credentials against approved access control lists and directories. This authentication matches a username with the endpoint making the request.

Security posture checks

In addition to login credentials, the system scans the endpoint to validate it complies with security standards like having the latest OS updates, corporate antivirus software installed, encryption enabled, etc. Devices that fail these checks can automatically be quarantined or blocked.

Access determination

With the user authenticated and the device validated, the NAC system determines whether to allow or deny network access. Access decisions tie to pre-defined user roles and access permissions. For instance, contractors may get Internet-only access while executives connect securely to corporate databases.

Ongoing session monitoring

Once a session starts, deeper traffic inspection capabilities allow NAC tools to continually monitor network activities for security risks. DLP scans can check for unauthorized data transfers. Behavioral analytics identify potentially compromised credentials.

Automated threat response

If a violation or threat surfaces, pre-configured controls enable NAC solutions to instantly respond. Notifications alert IT staff while automatic protections like session termination, interface shutdowns, or endpoint isolation activate within seconds.

Regular NAC policy optimization

Reviewing event and access logs lets administrators fine-tune NAC policies over time for maximum security and efficiency. For example, detecting numerous failed login attempts from a particular IP range may indicate hackers probing defenses and warrant permanently blacklisting those IPs.

Why is network access control important?

NAC is a vital aspect of network security for modern, dynamic business environments. As networks grow and support more flexible access models, the cyber attack surface expands. Without NAC, organizations lose visibility and control over who and what connects to the network. This leaves them vulnerable to threats like:

• Unauthorized users and devices
• Malware or ransomware attacks
• Non-compliant endpoints violating security standards
• Data exfiltration
• Insufficient support for regulations

Effective NAC mitigates these risks. Strict access policies block bad actors and vulnerable endpoints. Continuous compliance checks ensure devices adhere to security best practices. Monitoring tools detect unusual behavior that would indicate threats. Automated controls can instantly isolate impacted systems.

Put simply, NAC acts as a gatekeeper that lets authorized business flow securely while keeping dangerous elements out of the network. The foregoing risks pose not just security issues but also serious financial, legal, and reputational consequences. Investing in NAC represents a proven way to tackle network vulnerabilities.

Common use cases for network access control

IT teams leverage NAC solutions in diverse environments but tend to focus on a few key use cases:

Managing BYOD 

Bring-your-own-device (BYOD) policies that allow staff to access corporate networks through personal devices have grown exponentially. NAC is critical for securing BYOD. It verifies identities, checks devices for up-to-date software and security tools, and ensures compliance.

Onboarding third parties 

The need to temporarily accommodate partners, contractors, guests, and vendors is common. NAC allows IT staff to onboard external parties quickly through self-service portals with restricted network access.

Handling IoT expansion enterprise

IoT networks present visibility and security challenges. The rapid proliferation of connected devices makes keeping track of everything extremely difficult. NAC solutions provide comprehensive device inventories, automate monitoring and management, and enforce consistent policies.

Securing critical infrastructure

 In industries like energy, manufacturing, and transportation, NAC helps secure specialized equipment. It provides real-time network management essential to maintaining safe, reliable operations in complex physical environments.

Achieving compliance

For healthcare, finance, and other highly regulated sectors, NAC is an invaluable compliance aid. It provides the device visibility, access controls, and policy enforcement required to meet rigorous legal standards.

Enabling effective incident response 

NAC improves threat detection while enabling rapid, automated actions—like quarantining or disabling impacted systems—to isolate and mitigate cyber attacks. This limits damage and supports faster, more effective response.

Benefits and goals of network access control

NAC capabilities deliver considerable advantages:

Complete network visibility

By scrutinizing everything attempting access, NAC gives administrators greater awareness regarding the size, complexity, and vulnerabilities of the extended network environment.

Air-tight access policies

Role-based access tiers allow IT teams to fine-tune permissions for different users and devices. The principle of least privilege can be applied to minimize unnecessary access that attackers could exploit.

Instant device compliance

Checking credentials and security software constantly maintains compliance. Non-updated or vulnerable endpoints can be blocked immediately.

Accelerated threat response

Automated containment abilities allow NAC solutions to instantly neutralize detected threats without IT intervention. This reduces dwell time.

Optimized auditing and reporting

Detailed access logs support forensics, audits, and compliance reporting, providing evidence around network activities and security controls.

NAC strengthens virtually every aspect of network security—access, compliance, monitoring, incident response, and more. Implementing NAC should make networks incredibly hard to penetrate. As a result, organizations keep data, devices, and critical systems secure.

Network access control list

A network access control list (NACL) acts as the central policy definition regulating network access rights. NACLs are integral components that enable the core functionalities of NAC solutions.

NACLs consist of various protocols that:

• Authenticate user identities against directories like Active Directory or LDAP
• Validate device endpoint compliance against security benchmarks
• Authorize user and device access to network resources
• Restrict post-admission permissions to least privilege principles
• Detect policy violations or threat triggers from endpoints
• Trigger automated threat response actions like quarantines

Structuring NACLs using a role-based model improves efficiency and security. For example, the network admission policy for a finance team could require:

• Active Directory username/password authentication
• Multi-factor authentication via tokens
• Confirmation of device compliance with encryption standards
• Permission to access only finance databases and applications

While guest admission may involve:

• Self-service portal credential input
• Limited access to a segmented guest network
• Detailed activity logging for audit purposes

Cisco products like the Adaptive Security Appliance (ASA) rely on access control lists (ACLs) to filter traffic by user, group, IP address, protocol, port, and more. Integrating these Cisco ASA ACLs with the wider NAC solution’s allow lists facilitates consistent network access governance.

Adjusting NACL protocols allows IT administrators to continuously optimize network security. Adding, updating, and removing access protocols must be an ongoing process to respond to new threats, technologies, and business demands. Maintaining rigorous, tailored network access controls requires significant coordination between security and infrastructure teams.

How to create a network access control list

Establishing network access control lists requires carefully evaluating organizational needs, resources, risks, and capabilities. IT administrators should develop NACLs using the following best practices.

Catalog all assets

Gathering a comprehensive inventory of network-connected devices provides essential visibility. Discovery tools can automate the mapping of all users, endpoints, network segments, business systems, servers, and data repositories to protect the infrastructure.

Classify access requirements

Categorize access needs for each group based on their legitimate business functions using the principle of least privilege. Role-based access tiers enhance security by restricting unnecessary lateral movement. Leverage network automation to implement policies that dynamically adapt permissions as user responsibilities change.

Assess risk scenarios

Modeling potential attack pathways based on current vulnerabilities allows tailored access restrictions to shore up security gaps proactively. Ensuring NACL protocols align to the highest risks reduces the attack surface. Regularly penetration testing the network also exposes previous unknown weaknesses to address.

Detail compliance standards

Strictly adhere to all regulatory or internal policy compliance statutes related to data security, acceptable use policies, and privacy. Validate that NAC solution reporting and access logs meet auditing requirements as well.

Map network infrastructure

Catalog details regarding physical hardware, traffic flows, data types, and wired and wireless connections in the environment to comprehensively secure it. This supports appropriate network segmentation and building security into network infrastructure by design.

Select initial controls

Determine rigorous yet practical baseline access controls covering assets with high protection needs first, like customer databases. Implement monitoring and alerts for unusual access attempts. Plan incident response workflows for the containment of unauthorized users or devices.

Continually optimizing NACL protocols is essential as assets, data flows, threats, and regulations evolve across the business and technology landscapes. Also coordinate policy changes through security, networking, compliance, legal, and leadership teams. Evaluate the latest network security hacks threatening access controls and shore up deficiencies.

Effective NACL construction requires understanding key organizational risks, infrastructure intricacies, and security capabilities. Building a robust model for governance sets the stage for trusted network access and threat resistance. 

Review policies frequently as more smart devices connect to the network through IT/OT convergence. Rely on automation wherever possible so that distributed infrastructure at enterprise scale remains visible and protected.

Network access control solutions

Many network access control solution options are available on the market ranging from specialized products focused solely on NAC to broader network security platforms with integrated NAC capabilities. When evaluating solutions, IT teams need to weigh factors like integration complexity, TCO, and overall usability.

Deep integration without rip and replace 

You likely have effective security and network monitoring systems in place already. Strong NAC solutions will integrate with existing infrastructure seamlessly through open APIs rather than demand full-scale replacements. So, make sure to prioritize tools that allow simple, non-disruptive deployment.

Map network access to other security events 

Robust network modeling and mapping allow NAC systems to link suspicious access attempts with activity detected by other monitoring solutions. This facilitates automated, coordinated response across tools for faster threat neutralization.

Uncover all network blind spots 

NAC tools must maintain continuously updated inventories detailing every endpoint to ensure full network transparency. So, look for a solution with agentless device discovery protocols to fully expose infrastructure complexity, which permits stronger segmentation and access controls.

Empower least privilege access 

Identity-aware NAC solutions allow you to establish tiered access permissions by individual or role. Restricting user credentials and device capabilities limits unnecessary access that attackers exploit while enabling normal business functions. Therefore, a solution that enables you to apply least privilege access principles network-wide is essential.

Self-remediating access policies 

When applying initial NAC controls proves overly strict and blocks legitimate requests, cumbersome IT involvement to fix mistakes reduces operational efficiency. As a result, make sure to prioritize solutions with self-remediation capacities to resolve common access issues automatically.

Ongoing optimization and updating 

Access policies require continual adjustment for shifting network environments and new attack techniques. The strongest NAC platforms proactively notify administrators whenever updated protocols are required for requests involving new device types, unrecognized user credentials, emerging threats, or policy gaps.

When considering solutions, validate that prospective NAC platforms integrate sustainably with existing stacks and deliver intuitive, intelligent policy enforcement and reporting. Keeping control over network access as complexity increases is essential. The right NAC tools turn networks into well-regulated yet frictionless environments securing authorized connectivity.

Implementing network access controls

For organizations new to NAC, an incremental rollout focused on high-priority assets first is recommended to reduce risk. This phased approach gives IT administrators time to become intimately familiar with managing and supporting the new NAC systems before enforcing organization-wide policies.

Typical NAC implementation steps include:

1. Plan

Clearly detail all NAC requirements, controls, and responsibilities across security, IT, and business teams. Perform thorough cost-benefit and ROI analyses for different NAC solution options under consideration. Develop budget estimates over 3-5 years addressing upfront costs, licensing, maintenance, training, staffing implications, and more.

2. Test

Set up a trial NAC version covering non-essential network segments and user groups. Confirm system effectiveness for use cases like onboarding new devices or restricting application access. Evaluate usability and rule strictness to prevent productivity disruptions.

3. Deploy

Publish initial access control policies focused on high-security networks like customer data systems, financial reporting tools, and confidential databases. Use this phase to balance security with user experience before expanding.

4. Expand

Consistently apply NAC controls across additional infrastructure over 6-12 months. Gradually boost policy strictness to meet target enforcement levels.

5. Review

Continuously gather quantitative data like system logs and qualitative feedback through surveys and interviews. Monitor open tickets for access-related complaints. Keep policies nimble regarding new systems, dynamic compliance demands, and more.

An effective implementation requires clear change management planning and extensive user education. When network access functions alter dramatically for staff, confusion and productivity challenges can occur without sufficient communication and support. Consider change impact assessments, procedure documentation, training programs, and a user feedback process.

This expansion plan allows organizations to maximize benefits over time while ensuring smooth NAC deployments. IT administrators gain experience managing and tweaking NAC systems progressively rather than facing organization-wide enforcement from day one.

Following these best practices for layered rollout and continual optimization helps organizations implement network access control successfully.

NAC delivers air-tight yet frictionless security

With networks becoming more open and distributed, NAC’s access oversight and threat mitigation abilities are invaluable. Following the best practices around policy development, solution selection, and managed adoption covered here will help maximize benefits while ensuring smooth deployments.

Organizations that implement NAC thoughtfully gain peace of mind knowing their network security posture and resilience fundamentally improve. Even as networks grow infinitely more complex, NAC returns control and visibility for IT teams. Protecting infrastructure and data has never been more achievable.