Protecting Your Microsoft 365: Strategies Against On-Premises Threats

In today's digital landscape, where data breaches and cyber attacks are increasingly common, protecting your organization's Microsoft 365 environment is paramount. Microsoft 365 serves as the backbone of many organizations, facilitating communication, collaboration, and data management. However, the interconnected nature of on-premises and cloud systems poses unique security challenges. Recently, Microsoft released an insightful article titled "Protecting Microsoft 365 from on-premises attacks," shedding light on the vulnerabilities associated with on-premises environments and offering practical recommendations for safeguarding your Microsoft 365 cloud environment. Let's delve into the key insights and recommendations outlined in this article.

Understanding the Threat Landscape

Before diving into mitigation strategies, it's essential to understand the threat sources in on-premises environments. Hybrid deployments, which connect on-premises infrastructure to Microsoft 365, introduce potential vulnerabilities. Two primary threat vectors highlighted in the article are federation trust relationships and account synchronization. Federated trust relationships, such as SAML authentication, can be exploited if the token-signing certificate is compromised, granting attackers administrative access to your cloud environment. Similarly, account synchronization can lead to unauthorized modifications of privileged users or groups, posing a significant security risk.

Protecting Your Microsoft 365 Environment

To mitigate these threats effectively, Microsoft recommends adhering to a set of security principles illustrated in a reference architecture. Key recommendations include:

  1. Isolating Administrator Accounts: Admin accounts should be mastered in Microsoft Entra ID, authenticated using multifactor authentication, secured by Microsoft Entra Conditional Access, and accessed only via Azure-managed workstations. Additionally, no on-premises accounts should have administrative privileges in Microsoft 365.
  2. Managing Devices from Microsoft 365: Utilize Microsoft Entra join and cloud-based mobile device management to eliminate dependencies on on-premises device management infrastructure, reducing potential security risks.
  3. Limiting On-Premises Account Privileges: Ensure that on-premises accounts do not have elevated privileges in Microsoft 365 and that changes to these accounts cannot compromise your cloud environment's integrity.
  4. Implementing Cloud Authentication: Deploy passwordless authentication and multifactor authentication to strengthen credential security and reduce the risk of unauthorized access.
Specific Security Recommendations

The article provides specific security recommendations for implementing the aforementioned principles, including:

  • Isolating privileged identities and implementing just-in-time access using Microsoft Entra Privileged Identity Management.
  • Utilizing cloud authentication methods such as Windows Hello, FIDO2 security keys, and Microsoft Entra multifactor authentication.
  • Provisioning user access from the cloud to isolate potential on-premises compromises.
  • Leveraging cloud groups for collaboration and access management, decoupling these functions from on-premises infrastructure.
  • Managing devices from the cloud and migrating workload servers to Azure infrastructure as a service (IaaS) to reduce dependency on on-premises systems.
Monitoring and Logging

After implementing security measures, proactive monitoring and logging are essential to detect and respond to potential threats effectively. The article suggests monitoring scenarios such as suspicious activity, user and entity behavioral analytics (UEBA) alerts, emergency access account activity, and privileged role activity. Additionally, defining a robust log storage and retention strategy ensures that critical security events are captured and analyzed in a timely manner.


Securing your Microsoft 365 environment requires a comprehensive approach that addresses both on-premises and cloud-based vulnerabilities. By implementing the recommendations outlined in Microsoft's article, organizations can enhance their security posture and mitigate the risks associated with on-premises attacks. Protecting sensitive data and maintaining operational resilience are ongoing efforts that require continuous monitoring, adaptation, and collaboration across teams. Embracing a proactive security mindset is crucial in safeguarding against evolving cyber threats and ensuring the integrity of your Microsoft 365 environment.

For further details and actionable insights, I highly recommend reading the full article on protecting Microsoft 365 from on-premises attacks here.

This blog post provides a comprehensive overview of the key insights and recommendations from Microsoft's article on protecting Microsoft 365 from on-premises attacks. It emphasizes the importance of implementing proper security controls, user and identity management, monitoring, and logging to safeguard your organization's Microsoft 365 environment. If you have any questions or would like to share your thoughts on securing Microsoft 365, feel free to leave a comment below!

This article focuses on protecting Microsoft 365 from on-premises attacks by providing specific security recommendations and outlining threat sources in on-premises environments. Here are the main points to consider and implement in an EntraID environment:

  1. Threat Sources in On-Premises Environments:
    • Microsoft 365 benefits from extensive monitoring and security infrastructure but can be compromised through hybrid deployments connecting on-premises infrastructure.
    • Primary threat vectors include federation trust relationships and account synchronization, which can grant attackers administrative access to the cloud.
  2. Protection Strategies:
    • Disable federation trust relationships whenever possible to prevent unauthorized access through compromised SAML token-signing certificates.
    • Ensure synchronized objects from on-premises hold no privileges beyond a basic user in Microsoft 365.
  3. Specific Security Recommendations:
    • Isolate privileged identities by using cloud-only accounts, implementing just-in-time access with Microsoft Entra Privileged Identity Management (PIM), and providing the least privilege necessary.
    • Implement cloud authentication methods like Windows Hello, FIDO, or Microsoft Authenticator to reduce the risk of credential-based attacks.
    • Provision user access from the cloud using methods such as provisioning from cloud HR apps, cloud application provisioning, or Microsoft Entra B2B collaboration.
    • Use cloud groups for collaboration and access to decouple from on-premises infrastructure.
  4. Device Management:
    • Manage devices from the cloud by deploying Microsoft Entra joined Windows 10 workstations with mobile device management policies and using Windows Autopilot for automated provisioning.
    • Deprecate on-premises single-sign-on systems and migrate workload servers to Azure IaaS if feasible.
  5. Conditional Access Policies:
    • Use Microsoft Entra Conditional Access to interpret signals and make authentication decisions, including blocking legacy authentication protocols whenever possible.
  6. Monitoring and Log Management:
    • Proactively monitor the environment for suspicious activity, anomalous behavior, and changes to tenant-wide configurations using Microsoft Entra logs and Azure Monitor.
    • Implement a log storage and retention strategy to facilitate investigation and forensics, considering tools like Microsoft Sentinel.
  7. Next Steps:
    • Build resilience into identity and access management by further securing external access and integrating all apps with Microsoft Entra ID.

By implementing these recommendations, organizations can significantly reduce the risk of on-premises compromises impacting their Microsoft 365 environment.

Book a meeting with us now to get started with protecting your Microsoft 365 environment!


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