Microsoft 365 is extremely popular across various industries. It is often an organization's flagship application, containing valuable and critical information about its operations, employees, customers, and partners. Therefore, Microsoft 365 resilience and cybersecurity should be top priorities for any organization using it.
While Microsoft is responsible for securing the infrastructure and maintaining the application, the customer is the administrator and data owner. This means it is up to the client to properly secure their Microsoft 365 tenant.
In this article, I identify the most common concerns every organization should prioritize.
Data Exfiltration
Data exfiltration occurs when sensitive, confidential, or strategic data is illegally transferred from your Microsoft 365 environment to an external location, typically controlled by malicious actors. It can happen through misconfigurations, user negligence, malware, social engineering, or exploited security vulnerabilities.
Infected Files
Microsoft 365 allows users to sync files from their devices to the cloud (e.g., OneDrive libraries). If a local file is infected with malware, syncing can upload it to the cloud and potentially spread it to other devices.
Dormant or Unused Applications
Not all services included in a Microsoft 365 license are used. For example, your organization might frequently use Word, Excel, and SharePoint but rarely use OneDrive. Unused applications may still be vulnerable and should be restricted to minimize risk.
Unsecured Communication Channels
Phishing and malware remain common attack vectors, but others exist. Microsoft Teams, which can connect to external networks, can also be used to deliver ransomware or malicious content, especially if external messaging is enabled.
Sharing via Teams and SharePoint
SharePoint often stores sensitive information. Failing to secure access can expose this data, potentially violating privacy laws such as Quebec's Law 25. SharePoint, like Teams, allows external sharing, which can further increase risk.
Proliferation of Teams and Sensitive Data
Poor sharing practices, cluttered data, and lack of oversight over Teams and SharePoint increase the attack surface and risk of data leaks or compliance failures. Policies and regular data cleanup are essential.
Backups
Despite common beliefs, Microsoft 365 does not offer foolproof data protection. Risks like accidental deletion, limited retention, misconfigurations, and cyberattacks persist. External backups remain a best practice to ensure business continuity.
How to Stay Protected
Secure the Environment
Organizations can use resources like the CIS Benchmark for Microsoft 365 to apply essential security controls.
Promote a Proactive Cybersecurity Culture
Equip users with simple, fast tools that encourage awareness and make it easier to protect sensitive data.
Lifecycle Management for Teams and SharePoint
Securely archive unused libraries and empower resource owners to manage their own content.
Simplify Access Certification
Access reviews for Teams and SharePoint should be user-driven to ensure effective and decentralized permission control.
Manage External Users Carefully
External collaborators should have limited, controlled access. Employees must revoke access when collaborations end.
Monitor Sharing
Poor file-sharing practices can increase risk. Simple tools should be provided to users to manage shared content efficiently.
Conclusion
While Microsoft 365 is a powerful productivity suite, security is a continuous, shared responsibility. Maintaining a secure environment requires constant vigilance: access control, lifecycle management, and user awareness are all critical. Tools like MD.ECO Proactive Cybersecurity, which integrates with Teams, can help manage these risks. In the end, protecting a Microsoft 365 environment demands an ongoing, collaborative effort to ensure the security of critical data and operations.