Securing the Modern Workplace: Transitioning from Legacy Authentication to Conditional Access
Authored by: Gonzalo Brown Ruiz, Senior Microsoft 365 Engineer & Cloud Security Specialist Date: July 2025 Introduction In today’s threat landscape, legacy authentication is one of the weakest links in enterprise security. Protocols like POP, IMAP, SMTP Basic, and MAPI are inherently vulnerable — they don’t support modern authentication methods like MFA and are frequently targeted in credential stuffing and password spray attacks. Despite the known risks, many organizations still allow legacy authentication to persist for “just one app” or “just a few users.” This article outlines a real-world, enterprise-tested strategy for eliminating legacy authentication and implementing a Zero Trust-aligned Conditional Access model using Microsoft Entra ID. Why Legacy Authentication Must Die No support for MFA: Enables attackers to bypass the most critical security control Password spray heaven: Common vector for brute-force and scripted login attempts Audit blind spots: Limited logging and correlation in modern SIEM tools Blocks Zero Trust progress: Hinders enforcement of identity- and device-based policies Removing legacy auth isn’t a nice-to-have — it’s a prerequisite for a modern security strategy. Phase 1: Auditing Your Environment A successful transition starts with visibility. Before blocking anything, I led an environment-wide audit to identify: All sign-ins using legacy protocols (POP, IMAP, SMTP AUTH, MAPI) App IDs and service principals requesting basic auth Users with outdated clients (Office 2010/2013) Devices and applications integrated via PowerShell, Azure Sign-In Logs, and Workbooks Tools used: Microsoft 365 Sign-In Logs Conditional Access insights workbook PowerShell (Get-SignInLogs, Get-CASMailbox, etc.) Phase 2: Policy Design and Strategy The goal is not just to block — it’s to transform authentication securely and gradually. My Conditional Access strategy included: Blocking legacy authentication protocols while allowing scoped exceptions Report-only mode to assess potential impact Role-based access rules (admins, execs, vendors, apps) Geo-aware policies and MFA enforcement Service account handling and migration to Graph or Modern Auth-compatible apps Key considerations: Apps that support legacy auth only Delegates and shared mailbox access scenarios BYOD and conditional registration enforcement Phase 3: Staged Rollout and Enforcement A phased approach reduced friction: Pilot group enforcement (IT, InfoSec, willing users) Report-only monitoring across business units Clear communications to stakeholders and impacted users User education campaigns on legacy app retirement Gradual enforcement by department, geography, or risk tier We used Microsoft Entra’s built-in messaging and Service Health alerts to notify users of policy triggers. Phase 4: Monitoring, Tuning, and Incident Readiness Once policies were in place: Monitored Sign-in logs for policy match rates and unexpected denials Used Microsoft Defender for Identity to correlate legacy sign-in attempts Created alerts and response playbooks for blocked sign-in anomalies Results: 100% of all user and app traffic transitioned to Modern Auth Drastic reduction in brute force traffic from foreign IPs Fewer support tickets around password lockouts and MFA prompts Lessons Learned Report-only mode is your best friend. Avoids surprise outages. Communication beats configuration. Even a perfect policy fails if users are caught off guard. Legacy mail clients still exist in vendor tools and old mobile apps. Service accounts can break silently. Replace or modernize them early. CA exclusions are dangerous. Every exception must be time-bound and documented. Conclusion Eliminating legacy authentication is not just a policy update — it’s a cultural shift toward Zero Trust. By combining deep visibility, staged enforcement, and a user-centric approach, organizations can securely modernize their identity perimeter. Microsoft Entra Conditional Access is more than a policy engine — it is the architectural pillar of enterprise-grade identity security. Author’s Note: This article is based on my real-world experience designing and enforcing Conditional Access strategies across global hybrid environments with Microsoft 365 and Azure AD/Entra ID. Copyright © 2025 Gonzalo Brown Ruiz. All rights reserved.Building Enterprise-Grade DLP with Microsoft Purview in Hybrid & Multi-Cloud Environments
Authored by: Gonzalo Brown Ruiz, Senior Microsoft 365 Engineer & Cloud Security Specialist Date: July 2025 Introduction Data is the lifeblood of every modern organization, yet it remains one of the most exposed assets. As organizations embrace hybrid and multi-cloud models, traditional endpoint or email-only DLP solutions no longer provide sufficient protection. The explosion of data across Exchange, SharePoint, Teams, OneDrive, and third-party SaaS applications introduces new risks and compliance challenges. Microsoft Purview Data Loss Prevention (DLP) provides a powerful solution that unifies data governance, sensitivity labeling, and policy enforcement across your cloud ecosystem. However, building an enterprise-grade DLP strategy goes far beyond enabling policies. Why Traditional DLP Fails in Modern Environments Traditional DLP approaches often: Protect only endpoints or email without covering cloud services Lack integration with data classification and labeling frameworks Generate excessive false positives due to generic rule sets Create operational friction for end users In hybrid environments with Teams, SharePoint, and OneDrive, these limitations lead to fragmented coverage, compliance blind spots, and user workarounds that expose sensitive data. The Microsoft Purview Advantage Microsoft Purview DLP offers: Unified policy management across Exchange Online, SharePoint, Teams, and OneDrive Integration with Sensitivity Labels for data classification and encryption Real-time policy tips that educate users without blocking productivity Built-in compliance manager integration for audit readiness When architected properly, Purview becomes a strategic enabler of data governance and compliance rather than just a security checkbox. Key Components of an Enterprise-Grade DLP Strategy 1. Data Classification and Labeling Implement Sensitivity Labels with auto-labeling policies to classify and protect sensitive data at scale. 2. Policy Scoping and Exceptions Handling Design DLP policies that balance security with operational needs, incorporating exceptions for justified business processes. 3. Insider Risk Management Integration Correlate DLP events with insider risk signals to identify intentional or accidental data misuse. 4. Audit, Reporting, and Compliance Evidence Configure alerting, detailed reporting, and data residency mapping to fulfill regulatory and internal audit requirements. Implementation Framework: Your Step-by-Step Guide 1. Preparation Conduct a data inventory and sensitivity assessment Identify regulatory and contractual compliance obligations Engage business stakeholders for adoption readiness 2. Pilot Deployment Roll out policies to a controlled user group Review policy matches and refine rules to minimize false positives Provide targeted user training on policy tips and data handling expectations 3. Full Deployment Scale DLP policies across workloads (Exchange, SharePoint, Teams, OneDrive) Implement automated remediation actions with user notifications and audit logs 4. Optimization and Continuous Improvement Review policy match reports regularly to fine-tune thresholds and rules Incorporate feedback from security, compliance, and end users Integrate with eDiscovery workflows for legal readiness Best Practices and Lessons Learned Start with monitor-only policies to baseline activity before enforcing blocks Combine DLP with Sensitivity Labels and encryption policies for holistic protection Regularly educate users on data classification and handling standards Create clear governance structures for DLP ownership and policy management Balance security controls with user productivity to avoid shadow IT workarounds Conclusion Data Loss Prevention is no longer optional – it is a critical enabler of trust, compliance, and operational excellence. By architecting Microsoft Purview DLP as part of an enterprise data governance strategy, organizations can protect their most valuable asset – data – while empowering users to work securely and efficiently. Author’s Note: This article is based on my extensive professional experience designing and implementing Microsoft Purview DLP solutions for global enterprises across hybrid and multi-cloud environments. Copyright © 2025 Gonzalo Brown Ruiz. All rights reserved.Primer: How to Use RBAC for Applications to Control App Use of the Mail.Send Permission
The temptation to use the Mail.Send application permission in scripts can lead PowerShell developers into trouble because the permission allows access to all mailboxes, including sensitive executive and financial mailboxes. Fortunately, RBAC for Applications allows tenants to control the access that apps have to mailboxes and other Exchange content. All explained here with an example script to test RBAC of Applications. https://office365itpros.com/2026/02/17/mail-send-rbac-for-applications/New Outlook Gets Smarter DLP
The news that the new Outlook client will support custom oversharing dialogs for DLP policies might not seem very interesting, but it provoked me into looking more closely into how to build and deploy custom oversharing dialogs. All it takes is some well-structured JSON and an update to DLP rules, and the classic and Monarch Outlook clients should display custom tenant instructions to anyone who violates DLP rules. https://office365itpros.com/2026/02/12/custom-oversharing-dialog-dlp/How to Report DLP Alerts
MC1169572 announces that administrators can add classifications to DLP alerts to help with reporting. But how do you report DLP alerts? As it turns out, it’s relatively easy to retrieve DLP alerts via the Microsoft Graph Security API, and using the Get-MgSecurityAlertV2 cmdlet from the Microsoft Graph PowerShell SDK makes it even easier to find and report the data. https://office365itpros.com/2025/12/29/dlp-alerts-report/Purview Launches New DLP Policy to Control Copilot Prompts
A new DLP policy for Copilot prompts monitors blocked sensitive information types like credit card numbers to stop their use in Copilot prompts. The new policy can’t be combined with the existing DLP policy for Copilot, which checks for files with specific sensitivity labels to prevent Copilot using their content in its responses. But that’s OK because the two policies do very different work. https://office365itpros.com/2025/11/20/dlp-policy-for-copilot-prompts/
Compliance licenses at tenant level
Hi, We are a small organization of about 200 employees, and we have following requirements. DLP policies configuration at Exchange, OneDrive, SharePoint BYOD security Users should not be able to send files outside the org And so on as we evaluate We already have M365 Business Premium. However, after researching we figured out that M365 Business premium will alone not solve our requirements. May be compliance license will. We want to apply security policies at tenant level in our organization but definitely do not want every user to get licenses as this will be expensive for us and there is no requirement at all for our users. The question is, Is there a way to solve the above scenario?DLP Diagnostics Available in Purview Portal
DLP diagnostics were announced in October 2024, and it’s taken quite a while for Microsoft to make the four DLP diagnostic tests available. In truth, none of the tests are earthshattering and the kind of checking done by the tests could be performed quite easily by an experienced tenant administrator who knows the DLP solution. But those administrators are unlikely to be the target audience for these tests. https://office365itpros.com/2025/07/31/dlp-diagnostics-available/
Hidden Group and Hidden Group Membership
Hi everyone! I have come across a requirement where the client would like to use an excel spreadsheet, a service account and application registration to manage group membership for a confidential group. They would like to create a group from which the members cannot leave, see other team members and cannot see the group itself. Now, I have the concept of the flow with me but for the life of me, I cannot get around to finding/configuring a group that meets the requirement. Have you guys come across this sort of scenario? Group Configuration: Users should not be able to view the group Users should not be able to view members of the group Users should not be able to leave the group Thanks in advance.
