The Double-Edged Sword of Local Admin Rights - UNYK

Introduction

In many Windows domains, giving users local administrator rights on their PCs is seen as a quick fix for productivity. After all, with admin privileges users can install software or tweak settings without calling IT for every little request. However, this convenience comes at a steep cost to security. Granting regular users local admin rights (i.e. making their domain account a member of the local Administrators group on their machine) is like handing them – and potentially attackers – the keys to the kingdom. In this post, we’ll explore why no user should have unfettered admin access on their Windows workstation, the hidden risks and pitfalls of over-privileging, and best practices for implementing the principle of least privilege across your organization’s Windows environment.

What Are Local Administrator Privileges?

In Windows, a local administrator account has complete control over its PC. A user with local admin rights can install or remove software, change system configurations, create or delete user accounts, and modify security settings at will. Essentially, they own the endpoint – with the ability to alter any files or settings on that machine. By contrast, a standard (non-admin) user has far more limited permissions, typically restricted to running applications and changing only their own user preferences. Local admin rights are intended for IT staff or power users to perform maintenance, but when every user runs as an admin, it blurs the line between user and system controller.

It’s important to note that local admin privileges differ from domain admin privileges. A local admin’s power is supposed to be scoped to their individual PC, whereas a domain administrator can control settings and access across all computers in the domain. However, as we’ll see, a compromised local admin account on one machine can still facilitate attacks on the broader network. The practice of granting employees local admin access was once common (“this is how we’ve always done it”), but modern security threats have made this habit dangerously outdated.

The Security Risks of Giving Users Local Admin Rights

Handing out local admin rights to users dramatically increases the attack surface of your Windows environment. It’s not just a theoretical risk – attackers actively seek out machines where users have admin privileges because it makes their job much easier. Here are some of the key dangers when users operate as local administrators:

• Malware Installation and Execution: With full admin access, a user (or malware running under their account) can install any software, including malicious programs, without restriction. For example, an attacker who tricks an admin-privileged user into running a trojan can gain complete control of that PC – they could install ransomware that encrypts data, or covert backdoors that persist on the system. In fact, many malware strains require elevated privileges to fully compromise a machine; if the user is an admin, the malware can run with system-level power and dig its hooks in deeply without any UAC prompts or barriers.

• Disabling Security Measures: A local admin can disable or reconfigure critical security controls. An attacker who hijacks an admin user session could turn off antivirus and firewall protections, delete system logs to cover tracks, or alter security settings at will. This means malware or an intruder can operate undetected. Even well-meaning users with admin rights might inadvertently weaken security – for instance, by disabling endpoint protection because it slows their PC, or by turning off User Account Control (UAC) prompts. With standard user rights, such risky actions would be blocked by the OS.

• System-wide Changes and Exploitation of Vulnerabilities: Users with admin privileges can modify almost anything on the system (drivers, services, registry, etc.), which not only lets them “tune” their PC but also makes exploits far more effective. Vulnerabilities that might be harmless under a standard user can be weaponized if run with admin rights. One industry analysis estimated that over 90% of critical Windows vulnerabilities are exploitable only with administrative rights – meaning removing admin rights can mitigate the vast majority of Windows security bugs. In short, admin rights turn what would be minor annoyances into full-blown system compromises.

• Access to Other Users’ Data and Credentials: On a shared or domain-joined Windows machine, a local admin can read and manipulate files from other user accounts on that computer. More alarmingly, admin access allows dumping of credential material. Windows caches login credentials (password hashes, Kerberos tickets) in memory (LSASS) and on disk. A local admin can use tools like Mimikatz or CrackMapExec to extract these credentials. This might include passwords or hashes of other logged-in users, giving an attacker a stepping stone to impersonate higher-privileged accounts. For example, if a domain administrator ever logged into that workstation, an attacker with local admin rights could scrape the domain admin’s cached hash and essentially “pass-the-hash” to gain domain-wide access. One penetration test noted that a single compromised user account with local admin privileges was enough to obtain the hash of a domain admin, leading to complete takeover of the Active Directory environment.

• Lateral Movement Across the Network: Local admin rights make it far easier for an intruder to move laterally (from the initial infected host to others). If the same local admin credentials are used on multiple PCs, an attacker needs only to compromise one machine to start hopping to all the others. Unfortunately, many organizations still configure all their PCs with a common local administrator password for convenience. Attackers know this – it takes just one foothold to pass the hash or reuse stolen credentials on every other system with that shared admin account. Even unique credentials don’t fully solve it: if users are local admins of their own machines, an attacker can use that privilege to install remote access tools, create new admin accounts, or leverage tools like PsExec to pivot into other hosts on the same network segment. In one real-world example, a compromised user with local admin rights had access to a primary domain controller, giving attackers “keys to the kingdom” and control over all domain resources.

• “Weaponizing” the System Against Itself: An attacker (or malicious insider) with admin control can essentially turn a Windows PC into an offensive tool. They could load kernel drivers or rootkits, alter boot configurations, create hidden user accounts, or even encrypt the entire hard drive’s master boot record in seconds (see Cyberark article). They can also live off the land by using built-in admin tools for malicious ends – for instance, enabling services or scheduled tasks to maintain persistence, or using PowerShell and WMI to script attacks, all while blending in with normal admin activity. In short, once a standard user session is escalated to admin, virtually any malicious action on that system becomes possible.

It only takes one compromised admin-level account for an attacker to wreak havoc. As Microsoft’s security guides often reiterate: if a user with high privileges is tricked into running malware, that malware immediately gains the same level of control – whether that’s local admin on one PC or domain admin across all. By contrast, running as a normal user contains the blast radius; malware would be limited to that user’s own files and basic processes, unable to install drivers or access other hosts. Removing local admin rights won’t stop every attack, but it raises the bar so much that most attackers will move on to easier prey. As one cybersecurity expert put it, eliminating local admin rights and enforcing least privilege makes it significantly harder for adversaries to achieve their goals, to the point that the majority will “look elsewhere”.

Part 2 (Common Pitfalls of Over-Privileging Users) can be found here.