Microsoft continues to release frequent updates that reshape how organizations approach Microsoft 365 security. Recent announcements highlight how quickly vulnerabilities can emerge across cloud services, identity systems, and collaboration platforms.
For many businesses, the challenge is not just staying informed through Microsoft security news, but translating those updates into practical controls, monitoring and policy changes.
Read this post to understand how to turn the latest Microsoft security updates into meaningful improvements across your Microsoft 365 environment.
What's new in Microsoft 365 security
One of the most significant Microsoft 365 security changes in 2025 was the introduction of mandatory multi-factor authentication (MFA) for administrative accounts. Because credential theft remains one of the most common attack vectors, enforcing MFA significantly reduces the likelihood of unauthorized administrative access.
Microsoft reorganized its subscription tiers for 2026, integrating additional security capabilities into lower-tier licenses. At the same time, commercial pricing adjustments reflect the expanded set of built-in features. This shift signals a broader move toward embedding Microsoft 365 security as a standard component of the platform rather than an optional add-on.
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Defender for Microsoft 365, which was included in Plan 1, is now included in Microsoft 365 E3. This provides advanced anti-phishing protection, checking email attachments and real-time threat detection as a standard aimed to reduce Office 365 security issues.
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Safe links and URL checks are expanded to Microsoft 365 Business Basic and Standard to ensure frontline and small business users have active link protection in Outlook and Teams.
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Microsoft 365 E3 licenses now include Intune Remote Help and Advanced Analytics. At the same time, Microsoft 365 E5 users gained Endpoint Privilege Management and Cloud PKI, which allows them to manage identity trust without on-premises infrastructure.
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Starting in 2026, Security Copilot is built directly into the Microsoft 365 E5 tier, allowing security teams to use agentic artificial intelligence (AI) for automated incident investigation and response.
Microsoft's December 2025 Patch Tuesday rolled out important fixes for 57 vulnerabilities, according to Microsoft security news. Two critical-rated Remote Code Execution (RCE) flaws in Microsoft Office (CVE-2025-62554 and CVE-2025-62557) were patched. These were particularly dangerous as they could be triggered via the Outlook Preview Pane, meaning users didn’t even have to open the email to be compromised.
October 2025 Patch Tuesday was one of the largest release days of the last year. This security update addressed dozens of zero-day and critical issues across Windows and Azure components, which also impact Microsoft 365 security.
In addition, Microsoft fixed a large number of vulnerabilities, including:
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Zero-Day Office RCE (CVE-2025-59234) is a critical vulnerability in the core Office engine that was patched just as evidence of limited exploitation began to surface.
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Copilot Spoofing (CVE-2025-59252, 59272, 59286) is a new class of vulnerability. These allowed attackers to use prompt injection to trick the Microsoft 365 Copilot agent into revealing sensitive data or spoofing links to the user.
Shared responsibility: what Microsoft covers versus what you control
Microsoft 365 is delivered under a shared responsibility model, where Microsoft manages the security of the cloud infrastructure while customers remain accountable for protecting their data, identities, and configurations.
Microsoft is responsible for their datacenters, ensuring normal operation, redundancy, and failover in case of issues. Failover is initiated seamlessly for Microsoft 365 users. Microsoft is responsible for data protection and patching their components inside their datacenter, but not for protecting all end-user data.
Organizations and end-users using Microsoft 365 are responsible for what they store in Microsoft cloud services, how they configure retention settings, the data they create and delete, as well as the configuration of the Microsoft services they use. Backup responsibility is at the customer's side in this context. If customers accidentally delete files from their account or lose data due to ransomware, Microsoft is not responsible. That's why it is important to implement a reliable Microsoft 365 backup solution.
Office 365 security risks that persist
Even with regular Patch Tuesday updates, Office 365 security risks like misconfigurations, permission sprawl, and unprotected data remain widespread challenges. Administrators must check their security configurations and update them if needed. Assigning permissions beyond what users need to perform their roles expands the attack surface. If an endpoint is compromised, elevated privileges can make it easier for attackers to move laterally and access Microsoft 365 resources.
End of support for legacy platforms (e.g., Windows 10) increases exposure if not managed properly. As Windows security patches are provided only for extended support, not all users can install security patches on Windows 10. Cyberattackers can use new and unpatched vulnerabilities to infect computers running Windows 10 and gain access to Microsoft 365 data.
Practical Microsoft 365 security monitoring tips
With the massive volume of data generated by modern tenants, effective monitoring requires unified incident correlation and AI-driven tactics.
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Consider enabling Unified Audit Log, which is the most critical Microsoft 365 security monitoring asset. It records every significant action across Exchange, SharePoint, OneDrive and Teams. Ensure Unified Audit Logging is enabled.
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Set up a retention policy for Microsoft 365 logs. Standard licenses only keep logs for 90 days. For serious forensic investigations, you should aim for 180 to 365 days of retention.
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Think of Secure Score as your tenant's security credit score. This tool benchmarks your settings against Microsoft's best practices.
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Monitor risky or questionable sign-in events. Configure Conditional Access policies to flag such events.
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Audit global admin usage because the Global Administrator role is a high-value target. No one should be using this account for daily tasks. You can use privileged identity management to implement "just-in-time" access.
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Manual log analysis can be too slow nowadays. Use Microsoft Security Copilot, which is now built directly into the Microsoft 365 E5 tier, to help triage alerts. When a complex alert appears in Defender XDR, ask Copilot. For example: "Show me the lateral movement path for this incident and suggest a remediation script." This trick reduces the research time and helps identify the issue faster.
Microsoft 365 security best practices that work today
The most effective approach presumes checking security measures regularly and updating them if necessary. Regular configuration review is more than just a recommendation; it is a security requirement and an essential part of Microsoft 365 security best practices.
Use MFA to reduce the risk of phishing attacks. Starting in 2025, the MFA for Microsoft 365 is mandatory for administrator accounts. However, it is possible to enable this feature for regular users as well to improve overall security and reduce the attack surface.
Follow the least-privilege principle and configure only the permissions required to perform the needed task for a specific user. In this case, even if a user is compromised, the chances of an attacker getting "premium access" and compromising the entire organization are significantly lower. You can also use granular roles like Exchange Administrator or User Administrator instead of full Global Admin rights.
Conditional access is especially useful when users occasionally require elevated permissions but should not retain long-term administrative rights. This approach aligns with zero-trust principles, which require continuous verification of identity and context rather than implicit trust.
Security and compliance in Microsoft 365 are connected. Assign labels as security triggers and integrate them with conditional access policies. Auto-labeling driven by AI ensures that even if a user forgets to label a file containing critical information, the system automatically applies the "Confidential" shield. When it comes to M365 security and compliance, use data loss prevention features and proactive monitoring to achieve the best results. In addition, ensure your backup strategy aligns with data backup regulations in Europe to protect critical data and meet GDPR and local compliance requirements.
Protecting collaboration and identity
Microsoft collaboration tools like Teams and SharePoint have expanded security controls. Cybercriminals favor Microsoft Teams because they can use it for their social engineering schemes. For this reason, Microsoft has drastically enhanced its defenses to match the speed of modern attacks.
Safe Links for Teams provides URL protection and time-of-click verification. When a user clicks a link in a Teams chat, channel, or meeting, Microsoft Defender for Office 365 checks the URL against a real-time list of malicious sites. If the site is a known phishing page, the user is blocked.
The Safe Attachments feature can scan every file shared in Microsoft Teams. If malware is detected, the file is blocked or replaced with a "Malicious Attachment Blocked" placeholder. In addition, Microsoft 365 administrators can configure conditional access for external guests. In this case, a guest user must use phishing-resistant MFA to enter your Teams channels.
Microsoft 365 SharePoint is often used in combination with OneDrive and Teams. With new SharePoint security features, SharePoint sites can now be auto-labeled. If SharePoint detects sensitive data (like credit card numbers), it can automatically apply a label that restricts the site to Internal Only and blocks the Share to External button.
Anomaly detection is one of the most practical SharePoint features in terms of Microsoft 365 security. You can configure this feature for mass download alerts. For example, if a user suddenly downloads 500 files from a SharePoint site they have not visited in months, SharePoint alerts the security team and can automatically freeze the user's session.
Microsoft Azure Entra ID protection is the main component of Microsoft's zero-trust strategy. This feature utilizes AI and machine learning to analyze a large number of signals every day to detect threats in real-time and enforce adaptive authentication. You can use Conditional Access to manage adaptive authentication and change the login requirements based on the risk level. Entra ID Protection categorizes risk as user risk and sign-in risk. Moreover, Microsoft has introduced Identity Threat Detection and Response, which now includes specific detections for attacker-in-the-middle phishing and non-human identities.
Conclusion
Microsoft 365 security continues to evolve as new vulnerabilities, identity risks, and collaboration threats emerge. While regular updates strengthen the platform, effective protection depends on how well organizations implement controls, monitoring, and governance.
By combining Microsoft 365 security best practices with consistent review and policy alignment, businesses can reduce exposure and respond faster to emerging risks. Security updates are only as strong as the operational discipline that supports them.
