A Practical Guide to Least Privilege Access: Zero Trust Security in Action

Vulnerable machine identities now outnumber human users, attackers’ use of infostealers and access brokers is surging, and credential abuse remains the most common initial access vector for data breaches in 2025. It’s never been more important for organizations to enforce comprehensive least privilege – but that’s easier said than done.  

Enforcing least privilege security across sprawling enterprise networks takes more manual effort and resources than most security teams can spare. Over time, users accumulate access they no longer need, service accounts gain unchecked privileges, and legacy applications demand excessive permissions just to function.  

To clarify how teams of every size can automate least privilege access, we’ll take a deep dive into the principle of least privilege, how it relates to Zero Trust and compliance, and share best practices for making least privilege security practical and scalable.  

What Is the Principle of Least Privilege?  

The principle of least privilege (PoLP) is a security concept that states a user, process, or system should receive only the minimum level of access required to perform its intended function, and nothing more.  

Also called least privilege access, this principle was first discussed in the 1970s, when Jerome Saltzer wrote: “Every program and every privileged user of the system should operate using the least amount of privilege necessary to complete the job.”  

Several decades later, a variation of the principle was introduced by Gary McGraw and John Viega, who argued that it’s also key to limit how long privilege is available:  

Regardless of whether security teams take a traditional or dynamic approach to least privilege, it’s widely recognized as a foundational cybersecurity best practice. 

Why Is Least Privilege Important for Security?  

Nearly every major breach involves the abuse of privileged access. When three out of every four attacks now rely on valid credentials, the reality is that attackers no longer break in – they log in. Meanwhile, as rising identity-based attacks highlight a new security battleground, lax access controls and excessive permissions are no longer tenable.  

Implementing least privilege breaks the cycle of security breach and undetected lateral movement by:  

• Reducing the blast radius of an intrusion: Ensuring compromised accounts can only reach a limited number of assets 
• Preventing privilege escalation: Removing excessive admin rights and implementing additional just-in-time verification requirements  
• Improving granularity: Tying access activity to individual identities and operational needs

Privilege Creep: The Risks of Accumulated Access 

Privilege creep happens gradually. A user moves departments but retains old permissions “just in case.” Service accounts get quick exceptions to keep workflows running. IT teams grant local admin privileges to users who need to run legacy applications.  

Once granted, these privileges are rarely revoked; over time, they accumulate into a web of unmonitored permissions. When hackers gain an initial foothold in the network, those residual privileges become a launchpad for lateral movement.  

Mitigating privilege creep demands continuous enforcement, not one-time audits. When properly applied, least privilege access controls curb unmonitored privilege escalation and prevent lateral movement. 

Least Privilege Access and Zero Trust: How Are They Related?  

Zero Trust security is based on the philosophy “never trust, always verify.” Zero Trust upends traditional network security approaches by removing implicit trust and requiring continuous verification; enforcing least privilege by default is a core principle of Zero Trust.  

In other words, least privilege is a core element of the engine that powers Zero Trust. The relationship between the concepts can be broken down this way:   

• Zero Trust defines the mindset – never trust, always verify  
• Least privilege enforces the mechanics – grant only the access required, and only when it’s needed 

Importantly, modern Zero Trust architectures apply least privilege not only to human identities, but to machine-to-machine communications, APIs, and service accounts as well. Network segmentation, identity segmentation, and just-in-time multi-factor authentication (MFA) are the operational tools that make this possible. 

Enforcing Least Privilege for Cyber Compliance  

Almost every major cybersecurity regulation, industry standard, and cyber insurer explicitly or implicitly requires least privilege enforcement. For example, well-known cybersecurity regulations include compliance mandates like:  

• NIST Cybersecurity Framework (CSF): Access control category PR.AC-4 requires that organizations limit access to authorized users and processes only. Of all the functions identified in NIST’s framework, this is the one that Robert Bigman, the CIA’s first CISO, says security teams should prioritize.  
• NYDFS 23 NYCRR 500: Section 500.07 requires covered entities to restrict access privileges to ensure that employees, contractors, and systems can only access the information and systems necessary for their roles. Organizations must implement clear policies and technical controls to enforce access limitations.  
• PCI DSS: Requirement 7 mandates a “business-need-to-know” principle, stating that access to sensitive system components and cardholder data must be limited to those whose job requires it through role-based access controls. Additionally, Requirement 8.4 makes MFA non-negotiable for all access to cardholder data – even for internal personnel, systems, service accounts, and remote connections.  
• HIPAA: Section § 164.312(a)(1) on Access Control requires technical safeguards ensuring only authorized users can access electronic protected health information (ePHI); this means organizations must establish policies that limit access based on job function.  
• DORA: Builds on least privilege as a basis for information and communications technology (ICT) risk management and operational resilience across the EU financial sector. 

The common denominator across these and other frameworks? Granular access control and comprehensive least privilege enforcement. The same is true for cybersecurity insurance compliance – least privilege access has become a standard requirement for many carriers. 

How to Implement the Least Privilege Principle 

Implementing the principle of least privilege is foundational to bolstering overall security posture. The precise steps an organization takes to achieve least privilege may vary, but these best practices offer a blueprint for getting started.  

Audit Network Activity  

You can’t secure what you can’t see, so start with visibility. Comprehensive discovery of network activity – including communications between all network assets and identities – is essential to understand which connections are truly required. A period of monitoring also helps baseline normal behavior, making it easier to flag anomalies that indicate privilege misuse. 

Remove Unused Endpoints and Unnecessary Permissions  

Dormant accounts and outdated permissions are a silent liability. For example, only 2.6% of workload identity permissions are actually used, and 51% of workload identities are completely inactive. Pinpointing all network assets and identities then learning logon activities, account behaviors, and asset access patterns allows security teams to uncover these vulnerabilities. Removing inactive accounts, unnecessary ports, excessive permissions, and other gaps brings least privilege access within reach.  

Restrict Admin and Service Accounts to Operational Needs Only  

One of the most pressing challenges in identity security comes down to effectively securing admin and service accounts. This is particularly urgent as machine identities like service accounts – which are notoriously overprivileged, difficult to discover, and equally challenging to secure – now make up for over 70% of networked identities. Similarly, admin accounts with outstanding logon rights are a prime target for attackers with stolen credentials. To address these risks, admin and service accounts – along with all other identities – should be limited to approved actions or required assets and logon types with identity segmentation.  

Enforce Just-in-Time MFA for Privileged Access 

When privileged ports and protocols (like RDP, SMB, SSH, and others) remain open, attackers can easily traverse the network undetected but statically closing these ports can create operational disruptions. To maintain and strengthen least privilege access, keep privileged ports closed by default and enforce just-in-time verification with network layer MFA. This way, privileged ports only open after access is verified in real time – and only for as long as necessary – which eliminates excessive admin rights. This same approach should be leveraged any time privileged accounts attempt to access sensitive systems, adding an additional layer of identity security.  

Automate Dynamic Access Policy Creation and Enforcement 

Manual least privilege access policy management isn’t scalable in today’s enterprise environments. Instead, policy creation, maintenance, and enforcement should be automated to ensure access policies don’t become outdated as network changes occur, leaving gaps for attackers to slip through. With deterministic, accurate automation, security teams can build a self-maintaining least privilege posture.  

Proactively Enforce Least Privilege at Scale with Zero Networks  

Traditionally, organizations have relied on manual policy creation, static firewalls, and endless exception lists to enforce least privilege – all of which introduce friction without delivering comprehensive coverage. With Zero Networks’ automated, identity-aware microsegmentation, it’s easier than ever to enforce least privilege and achieve Zero Trust at scale.  

Zero Networks operationalizes the principle of least privilege across every axis of network traffic:  

• Automated microsegmentation isolates every asset within its own secure perimeter, closing unnecessary communication paths and blocking unauthorized lateral movement without disrupting operations. 
• Identity segmentation enforces granular access rules for users, devices, and applications, ensuring every connection is explicitly authorized to stop privileged account abuse.  
• Just-in-time network-layer MFA adds adaptive authentication at the exact moment of privileged access, turning static permissions into temporary elevated access.  
• Deterministic, highly accurate automation learns all network behavior to create and enforce least privilege policies at scale – no costly agents or manual tuning required. 

By unifying these capabilities into a single, agentless solution, Zero Networks turns comprehensive least privilege principle to practice. Learn how you can automate least privilege at scale with Zero Networks – request a demo.