Evaluating Ransomware Threats in Your M365 Environment

There are several straightforward steps you can take to assess your environment for vulnerabilities. You should:

1. Audit access points: Identify how users access M365 services, including browser, mobile, and third-party integrations. Pay close attention to guest access and legacy authentication.
   
2. Review phishing test results: Use results from internal phishing simulations to measure user risk. High click rates can highlight weak points in user awareness or security posture.
   
3. Check retention settings: Review retention policies across Exchange, OneDrive, and SharePoint. Align them with legal and operational requirements.
   
4. Simulate a restore: Run a recovery test to see what data you can recover, how long it takes, and where gaps exist. This helps validate your recovery plan.
   
5. Assess API limitations: Microsoft Graph API limits can slow large restores. Understand how these limits affect your recovery time.

Feature	Built-in Capability	Managed Solution Benefit
Retention Periods	Limited (30–93 days)	Extended, customizable retention options
Restore Granularity	Folder- or site-level only	File-, email-, and item-level restores
Immutable Storage	Not supported	Write-once storage to help reduce tampering risks
Teams & Planner Backup	Partial or unsupported	Full backup and restore for Teams, Planner, and more
Air-Gap Protection	Not available	Isolated storage that helps reduce ransomware impact
Automation & SLA Management	Manual and limited	Policy-driven, automated backup and recovery
Compliance & eDiscovery	Basic tools with export requirements	Integrated tools for compliance and audit trails

A focused backup and recovery strategy for M365 helps fill the gaps left by native protections. It gives organizations better control over their data, improves recovery time, and supports long-term retention and compliance.

Implementing Key Security Measures in M365

Here are some actions you can take to help protect your M365 environment:

1. Enable MFA for all users.
   Use Microsoft Entra ID to require MFA for all accounts, including admins and service accounts. Create conditional access policies to enforce this requirement organization-wide.
   
2. Configure Safe Links and Safe Attachments.
   In Microsoft Defender for Office 365, enable Safe Links to scan and rewrite URLs. Turn on Safe Attachments to analyze files in a sandbox before delivery.
   
3. Restrict global admin roles.
   Review admin role assignments in Entra ID. Use least privilege principles and enable just-in-time access through Privileged Identity Management for sensitive tasks.
   
4. Set up conditional access policies.
   Require trusted devices, block legacy authentication, and apply location-based restrictions. These policies help control access based on real-time risk.
   
5. Use modern authentication only.
   Disable legacy protocols like POP and IMAP. These are vulnerable to password spray attacks and do not support MFA.
   
6. Monitor access and sign-in logs.
   Regularly check logs in the Microsoft 365 Security & Compliance Center. Look for patterns like failed logins, unusual IP addresses, or abnormal file activity.

Methods to Enhance Ransomware Resilience

Reducing ransomware risk across Microsoft 365 requires more than just backup. Once inside, attackers often move laterally and target shared data and privileged accounts. Segmenting workloads by function and sensitivity helps contain the impact and limits access to business-critical systems.

Network segmentation helps isolate high-value data such as finance, HR, or legal content from general user traffic. This approach helps reduce the chance that malware spreads beyond the initial point of compromise.

Advanced threat protection tools help detect suspicious behavior early by analyzing login activity, file access, and user behavior. These tools rely on threat intelligence and anomaly detection to identify signs of compromise that standard filters and rules might miss.

1. Review Microsoft Entra ID sign-in logs.
   Filter for failed login attempts, unfamiliar IP addresses, and unknown devices. Look for patterns that could indicate brute force or credential stuffing.
   
2. Audit privileged roles.
   List all accounts with global admin or high-level permissions. Remove any unnecessary assignments and set up just-in-time access for sensitive tasks.
   
3. Check conditional access policies.
   Confirm policies are in place to require MFA, block legacy protocols, and restrict access based on location or device compliance.
   
4. Inspect SharePoint and OneDrive sharing settings.
   Identify any files or folders shared with anonymous links or external users. Remove access that is no longer needed.
   
5. Scan mailbox rules and forwarding settings.
   Look for rules that forward emails externally or automatically delete messages. These can be signs of account takeover.
   
6. Test data loss prevention policies.
   Simulate actions that should trigger DLP protections and verify that alerts are created. Confirm that enforcement actions work as configured.
   
7. Document findings and assign follow-ups.
   Track identified issues, assign owners, and set clear deadlines. This helps maintain accountability across teams and supports continuous improvement.