The Least Privilege Gap: Why Microsoft 365 Identity Security Remains a Critical Vulnerability

In the realm of modern IT governance, the Principle of Least Privilege (PoLP) is no longer a suggestion—it is a foundational requirement. The concept is simple: give users, applications, and service accounts only the minimum level of access necessary to perform their jobs. Yet, in the complex ecosystem of Microsoft 365, a dangerous chasm has opened between this Zero Trust doctrine and operational reality.

Despite widespread agreement on its importance, the implementation of PoLP is frequently stalled by “permission debt,” role fragmentation, and a systemic failure to manage non-human identities. The result is a massive, dormant attack surface that cybercriminals are increasingly adept at exploiting.

The State of Cloud Privilege: An Ocean of Unused Access

The data regarding cloud identity permissions reveals a systemic failure in access management. According to the Microsoft 2024 State of Multicloud Security report, out of 51,000 permissions granted to human and machine identities in cloud environments, only 2% are actually used. The remaining 98% represent a dormant attack surface—rights with no operational utility that provide attackers with disproportionate access if a account is compromised.

This issue is further compounded by the rise of “super identities.” The same Microsoft report found that more than 50% of cloud identities had access to all permissions and resources.

The Human Element: Over-Privileged Administrators

Within Microsoft 365 tenants, the situation remains precarious. Research indicates that 57% of organizations have over-privileged administrators. While 61% of tenants have limited their Global Admins to five or fewer (aligning closer to the CIS/Microsoft recommendation of two to four), a worrying 20% still have ten or more. In some extreme cases, companies have assigned the Global Administrator role to over 100 people.

The risk here is absolute: a Global Administrator has nearly unlimited power, including the ability to access any mailbox, modify security policies, and create backdoors.

The Silent Threat: Machine Identities

While human accounts get the most attention, non-human identities are the true blind spot. The CyberArk 2025 Identity Security Threat Landscape report reveals a staggering ratio of 82 machine identities for every one human identity. Despite this, 88% of organizations still define a “privileged user” as exclusively human.

The danger is significant: 42% of machine identities possess privileged or sensitive access. 51% of tenants have more than 250 applications with read-write permissions, some of which possess capabilities equivalent to a Global Administrator.

Why the Principle of Least Privilege Remains Elusive

If the risks are so clear, why is PoLP so difficult to enforce? The obstacles are rarely just technical; they are organizational and cultural.

• Complexity of the Role Model: Entra ID features over 100 built-in roles, 28 of which are marked as “privileged.” The split between Entra ID roles, service-specific roles (Exchange, SharePoint, Teams), and Azure RBAC creates chronic confusion. 62% of organizations believe the native Microsoft model is too complex to manage effectively, according to 2025 data from CoreView.
• Permission Debt: Environments become over-privileged over time. Temporary access granted for an urgent project, migrations, or poorly handled employee offboarding lead to an accumulation of rights that are never revoked.
• Security vs. Productivity: Restricting privileges creates operational friction. When administrators must request elevation for every action, productivity slows. In the daily tension between security and speed, convenience often wins—until a breach occurs.
• Non-Human Neglect: Service principals and API keys don’t take vacations or resign. Their permissions often remain active indefinitely, and their secrets are frequently renewed without reviewing whether the original level of access is still required.

How Attackers Exploit Excessive Privilege

Modern attackers rarely rely on sophisticated malware to enter a system; instead, they use legitimate credentials to “live off the land.” The CrowdStrike 2025 Global Threat Report found that 79% of cyber-intrusions in 2024 involved no malware at all. Attackers enter with valid credentials and then explore available permissions to escalate their privileges.

The speed of these attacks is alarming. The average time for lateral movement has dropped to 48 minutes, with records as low as 51 seconds. Privilege escalation is now a feature in 68% of ransomware attacks.

Case Study: Midnight Blizzard

The January 2024 Midnight Blizzard incident (as documented by MSRC) serves as a textbook example of privilege exploitation. The attacker didn’t find a technical flaw; they found a test account with a weak password and no multi-factor authentication (MFA). From there, they leveraged a legacy OAuth application that had been created years prior for a temporary need but was never decommissioned.

This forgotten application provided a bridge to the “full_access_as_app” role on Exchange Online, granting the attackers access to the mailboxes of Microsoft’s senior leadership. The breach was not the result of a sophisticated exploit, but of “permission debt.”

The Path to Total Control

Security researchers (Semperis, 2024) have demonstrated that an Entra application with the AppRoleAssignment.ReadWrite.All permission can self-assign the RoleManagement.ReadWrite.Directory role and subsequently promote itself to Global Administrator without any human intervention. This turns a seemingly minor permission into total tenant control.

The Regulatory Shift: From Best Practice to Legal Mandate

The drive toward least privilege is now being codified into law. Regulatory bodies are no longer treating Zero Trust as an option, but as a requirement for compliance.

• NIS2: Articles 18 to 22 explicitly mandate access control policies, the application of least privilege, and a strict separation between standard user accounts and administrative accounts.
• ANSSI: In June 2025, the French National Cybersecurity Agency (ANSSI) published guide PA-111, “Zero Trust Model – The Fundamentals,” reaffirming that no entity should be trusted by default and that constant monitoring and strict account tiering (per guide PA-022) are essential.
• Gartner’s Outlook: Gartner predicted in 2023 that by 2026, only 10% of large enterprises would have a mature, measurable Zero Trust program. This highlights a massive gap in readiness as we enter 2026.

Conclusion: A Challenge of Culture, Not Technology

The tools to solve the privilege crisis already exist. Microsoft provides PIM for Just-In-Time access, Entra Administrative Units for segmentation, and custom roles for granularity. The real challenge is organizational.

Moving toward a true state of least privilege requires breaking long-standing habits—like granting Global Admin rights “because it’s easier” or keeping access “just in case.” Organizations that treat privilege governance as a continuous discipline rather than a one-time project will not only be more resilient against identity-based attacks but will be the only ones prepared for the rigorous audits of NIS2 and DORA.

Frequently Asked Questions

What is the “Principle of Least Privilege”?
It is the security practice of limiting user and application access rights to the bare minimum necessary to perform a specific task, reducing the risk of accidental or malicious damage.

Why are machine identities more dangerous than human identities?
Machine identities (like apps and service principals) often have static permissions that never expire, don’t use MFA, and are frequently overlooked during security audits, making them ideal targets for attackers.

How does the Midnight Blizzard attack relate to least privilege?
The attack succeeded because a legacy application had excessive privileges that were no longer needed for any business purpose, providing the attacker an easy path to escalate their access.