Microsoft Defender for Office 365: Migration & Onboarding
This blog covers four key areas that are frequently missed, but they are essential for a secure and auditable deployment of Defender for Office 365. Before diving into the technical details, it is important to clarify a common misconception about Defender for Office 365 protections. Blocking Malicious File Downloads in SharePoint and OneDrive A common assumption during onboarding is that Microsoft Defender for Office 365 protections only apply to email. In reality, Safe Attachments also integrates with SharePoint Online, OneDrive for Business and Microsoft Teams. It scans files for malware even after they are uploaded or shared internally. However, this protection is only effective when the configuration explicitly prevents users from downloading files flagged as malicious. Without this setting, files detected as threats can still be downloaded locally. This creates a major risk particularly if the malware is detected post-delivery. In one investigation, I found that this setting had been left at its default, allowing users to download malicious files from SharePoint. This oversight created a significant exposure risk until it was corrected. This setting is part of the Safe Attachments for SPO/ODB policy and is critical in reducing internal exposure. Once enabled, this setting protects users in real time and acts as a powerful audit point. If someone disables this setting, whether intentionally or by accident, that action is recorded in Purview's Unified Audit Log under the DisallowInfectedFileDownloadDisabled operation. The video below offers a brief walkthrough on how to enable the setting, details the associated audit log events, and provides guidance on configuring alerts for any modifications: Regularly auditing for this event can help identify misconfiguration or potentially malicious administrative activity that could indicate insider threat behaviour. Including this check as part of your continuous security monitoring process is a smart, proactive move. Learn more at Step 2: (Recommended) Use SharePoint Online PowerShell to prevent users from downloading malicious files Once you have established protection against malicious files, the next step is ensuring your tenant is correctly set up to create and manage threat policies. Ensuring Organization Customization is Enabled A frustrating yet common hurdle during Defender for Office 365 onboarding is the inability to create threat policies such as anti-phishing or Safe Attachments policies. This confusion often stems from a basic configuration oversight: the tenant has not been enabled for organization customization. Without this step, the Microsoft 365 platform prevents the creation or editing of many critical security policies in Defender for Office 365. A few years prior with a new client being onboarded to Defender for Office 365, I encountered a situation where policy creation kept failing because this step wasn’t followed. It caused unnecessary delays and frustrated the security team until we identified the missing customization. The fix is simple. Run the Enable-OrganizationCustomization PowerShell cmdlet from Exchange Online. It is a one-time configuration task, but it is essential for policy management and overall service functionality. Including this step early in your deployment or migration plan prevents unnecessary delays and ensures the security team can fully leverage Defender for Office 365's capabilities from day one. This is particularly important for consultants who are brought in to assist after issues have already arisen. Getting ahead of this configuration means one less troubleshooting rabbit hole. With customization enabled, you can now take advantage of the preset security policies to quickly build a solid baseline. Using Preset Security Policies for a Strong Starting Point One of the best tools Microsoft has provided for onboarding is the Preset Security Policies feature. These come in two flavors: Standard and Strict. Figure 4 - Defender for Office 365 Preset security policies (Standard & Strict protection) They represent Microsoft’s recommended baseline configurations for anti-malware, anti-phishing, and spam protection. Learn more at Preset security policies in cloud organizations. For customers with limited security maturity or time to deeply understand the inner workings of Defender for Office 365, these presets are a game-changer. Figure 5 - Microsoft recommendation is to apply standard protection to all users In several cases, I have seen organizations with limited security teams benefit from activating these presets early. This approach gave them immediate protection while freeing up time to better understand and tune policies over time. For incident response, having a consistent and known-good baseline also helps reduce noise and false positives in the initial stages of deployment. Figure 6 - Apply strict Defender for Office 365 protection for priority users After setting foundational policies, controlling who has access to what within Defender for Office 365 is crucial to maintaining a secure environment. Implementing Unified RBAC for Least Privilege Access As more business units engage with Defender for Office 365 for everything from investigation to reporting, it is important to ensure each role has access only to what they need. Unified Role-Based Access Control (RBAC) in Defender for Office 365 makes this possible by allowing granular control over who can see and change what within the security portal. Figure 7 – Example least privilege role configuration for a Defender for Office 365 Incident Responder (image trimmed). This becomes critically valuable in larger or more complex organizations where responsibilities are split between security, compliance, IT, and operations teams. Figure 8 - Activating Microsoft Defender for Office 365 Workload in Defender XDR Roles. By using unified RBAC, you can avoid the dangerous and often default behavior of assigning Security Administrator rights to everyone involved. Instead, define roles based on function. For example, Tier 1 analysts might only need view and investigation access, while admins can manage policies. Figure 9 - Assigning a user to a Custom Microsoft Defender for Office 365 role, Entra Security Groups are also supported. This approach aligns with zero trust principles and makes it easier to audit who has access to sensitive areas. During onboarding, I recommend mapping stakeholders to the available roles and applying this model as early as possible. This helps establish accountability and improves your security posture before an incident occurs. Learn more at Map Defender for Office 365 permissions to the Microsoft Defender XDR Unified RBAC permissions Having set the right roles and permissions, it is vital to understand how these configurations contribute to a resilient and well-prepared security posture. Final Thoughts Successful onboarding to Microsoft Defender for Office 365 is not just about flipping switches. It is about making intentional configuration choices that support operational efficiency and long-term security goals. The points covered here are often missed in quick start guides but they are essential for building a solid foundation. Those who invest time in proper configuration are far better prepared when incidents arise. Migration is just the beginning. Set up Defender for Office 365 right to reduce risk and build real resilience. Please take two minutes to take this survey to let us know what you think of this blog (series), video, and community content. Questions or comments on this blog "Microsoft Defender for Office 365 Migration & Onboarding" for the author or other readers? Please log in and post your response below! _____________ This blog has been generously and expertly authored by Microsoft Security MVP, Purav Desai. with support of the Microsoft Defender for Office 365 product team. Lead M365 Incident Responder, Financial Services | Dual Microsoft Security MVP Learn More and Meet the Author 1) December 16th Ask the Experts Webinar: Microsoft Defender for Office 365 | Ask the Experts: Tips and Tricks (REGISTER HERE) DECEMBER 16, 8 AM US Pacific You’ve watched the latest Microsoft Defender for Office 365 best practices videos and read the blog posts by the esteemed Microsoft Most Valuable Professionals (MVPs). Now bring your toughest questions or unique situations straight to the experts. In this interactive panel discussion, Microsoft MVPs will answer your real-world scenarios, clarify best practices, and highlight practical tips surfaced in the recent series. We’ll kick off with a who’s who and recent blog/video series recap, then dedicate most of the time to your questions across migration, SOC optimization, fine-tuning configuration, Teams protection, and even Microsoft community engagement. Come ready with your questions (or pre-submit here) for the expert Security MVPs on camera, or the Microsoft Defender for Office 365 product team in the chat! REGISTER NOW for 12/16. 2) Additional MVP Tips and Tricks Blogs and Videos in this Four-Part Series: (This post) Microsoft Defender for Office 365: Migration & Onboarding by Purav Desai Safeguarding Microsoft Teams with Microsoft Defender for Office 365 by Pierre Thoor You may be right after all! Disputing Submission Responses in Microsoft Defender for Office 365 by Mona Ghadiri Microsoft Defender for Office 365: Fine-Tuning by Joe Stocker Learn and Engage with the Microsoft Security Community Log in and follow this Microsoft Defender for Office 365 blog and follow/post in the Microsoft Defender for Office 365 discussion space. Follow = Click the heart in the upper right when you're logged in 🤍 Learn more about the Microsoft MVP Program. Join the Microsoft Security Community and be notified of upcoming events, product feedback surveys, and more. Get early access to Microsoft Security products and provide feedback to engineers by joining the Microsoft Customer Connection Community. Join the Microsoft Security Community LinkedIn
Built-in report button is available in Microsoft Outlook across platforms
Outlook and Defender for Office 365 are excited to announce the release of built-in report button in Microsoft Outlook across platforms (web, new Outlook for Windows, classic Outlook for Windows, Outlook for Mac, Outlook for Android, Outlook for iOS, and Outlook for android Lite) for both personal and commercial accounts. You can find the built-in button across Outlook: Outlook on the web. New Outlook for Windows. Outlook for Mac version 16.89 (24090815) or later. Classic Outlook for Windows version Current channel: Version 16.0.17827.15010 or later. Monthly Enterprise Channel: Version 16.0.18025.20000 or later. Semi-Annual Channel (Preview): Release 2502, build 16.0.18526.20024 Semi-Annual Channel: Release 2502, build 16.0.18526.20024 Outlook for iOS version 4.2511 or later and Outlook for Android version 4.2446 or later. Outlook for Android Lite Benefits the built-in report button provides for security admins It works out of the box with no setup required The reporting experience for end user is the same across consumer and commercial accounts The report button is consistent across Outlook clients The report button is front and center on all clients The report button is present on the grid view, reading panel, preview panel, context menu The report button enables the user to select in bulk and report messages at once You can turn on and off the pre and post reporting popups for users in your organization using You can customize the individual pre and post reporting popup by adding text and links in 7 diff languages The report button is present on shared and delegate mailboxes enabling end users to report emails. Now present on outlook for web, new outlook for windows, outlook for mac, outlook for android and outlook for iOS The end user reports made by these clients are routed as per the message reported destination configured in the user reported settings. You can view the user report as soon as they are made on the If you have configured Microsoft only or Microsoft and my reporting mailbox in the user reported settings, the result from Microsoft analysis are available on the result column You can turn off the built-in report button on user reported settings by Selecting non-Microsoft add-in button and providing the address of the reporting mailbox of the 3 rd party add-in, or Deselecting monitor reported messages in outlook Note: The report phish add-in and the report message add-in does not provide support for shared and delegate mailbox. The report phish add-in, the report message add-in, and the built-in report button all read from the same user reported settings and use the same internal reporting API. In a way there are two different doors (entry point) to the same house (the backend). For the moment, the report message and report phish add-in are in maintenance mode to provide enough time for customers to migrate to the built-in button. To learn more, please check out Transition from Report Message or the Report Phishing add-ins - Microsoft Defender for Office 365 | Microsoft Learn Report phishing and suspicious emails in Outlook for admins - Microsoft Defender for Office 365 | Microsoft Learn User reported settings - Microsoft Defender for Office 365 | Microsoft Learn Protect yourself from phishing - Microsoft Support Report phishing - Microsoft Support How do I report phishing or junk email? - Microsoft SupportDoes Rights Management Service currently support MFA claims from EAM?
We've been testing EAM (external authentication methods) for a few months now as we try to move our Duo configuration away from CA custom controls. I noticed today that when my Outlook (classic) client would not correctly authenticate to Rights Management Service to decrypt OME-protected emails from another org. It tries to open the message, fails to connect to RMS, and opens a copy of the email with the "click here to read the message" spiel. It then throws a "something is wrong with your account" warning in the Outlook client's top right corner. If I try to manually authenticate & let it redirect to Duo's EAM endpoint, it simply fails with an HTTP 400 error. When you close that error, it then presents another error of "No Network Connection. Please check your network settings and try again. [2603]". I can close/reopen Outlook and that warning message in the top right stays suppresses unless I attempt signing into RMS all over again. However.. If I do the same thing and instead use an alternate MFA method (MS Authenticator, for example), it signs in perfectly fine and will decrypt those OME-protected emails on the fly in the Outlook client, as expected. I verified that we excluded "aadrm.com" from SSL inspection and that we're not breaking certificate pinning. So all I can assume at the moment is that Rights Management Service isn't honoring MFA claims from EAM. Any experience/thoughts on this? Thanks in advance!
Disabling PIN-based login on Entra-joined PCs
Hi guys. Yesterday I took two machines off the domain and Entra joined them. The goal was 1) remove their access to domain resources 2) have tenant users login to the machine and get enriched tokens every time. this works as desired. The problem is every user gets prompted to set a pin. these are both shared secondary/tertiary PC's - there is no point to having a 6 digit PIN on them. I thought the new Authentication Methods tools had controls for this, but apparently not. A script was run to change certain related Reg Keys (by my onsite tech) but this had no change on reboot. textreg add "HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\PassportForWork" /v Enabled /t REG_DWORD /d 0 /freg add "HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\PassportForWork" /v DisablePostLogonProvisioning /t REG_DWORD /d 1 /f HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\PassportForWork Enabled key was set to 0, and DisablePostLogonProvisioning was set to 1. These are from various help threads I found here and other resources. Unfortunately, they do not work. Not sure what to do here. I've read there are InTune controls for this - but I don't really have the time to work out WindowsPC ennrollment profiles for 2 machines. The site has InTune, but only for iOS mobile management. Thoughts?Join Merill Fernando and other guests for our Identity and Network Practitioner Webinar Series!
This October, we’re hosting a three-part webinar series led by expert Merill Fernando for Identity and Network Access practitioners. Join us as we journey from high-level strategy to hands-on implementation, unifying identity and network access every step of the way. Each session builds on the last, helping you move from understanding why a unified approach matters to what are the foundations to get started, and finally to how to configure in practice. The goal is to equip you with actionable skills, expert insights, and resources to secure your organization in a unified, Zero Trust way. Register below: Identity and Network Security Practitioner Webinar Series | Microsoft Community HubMarking Quarantine Notice senders as safe for entire tenant
Our users get quarantine notices weekly. They're configured to come from mailto:email address removed for privacy reasons (the domain specific to tenant).. sometimes they come from mailto:email address removed for privacy reasons anyways, but this is fine. The thing is, I end up with a LOT of users who end up receiving these in their junk mail. We have a lot of tenants - I don't really have the time to keep checking them, taking action on mis-junked items. Most stuff is configured to go to quarantine anyway. What's the best way to allow these senders? The IB Anti-Spam safe-senders component is not Secure-Score recommended, and we try to keep these scores high. But the tenant allow/block list allows a max of 45days since last use. There's so many options, I'm a little confused as to what's 'right' Thanks
user-reported phishing emails
Dear Community I have a technical question regarding user-reported emails. In Defender, under “Action and Submissions” -> “Submissions,” I can see the emails that users have reported under the “user reported” option. There, we have the option to analyze these emails and mark them as “no threats found,” “phishing,” or “spam.” The user is then informed. Question: Do these reported emails remain in the user's inbox when they report them? If not, do we have the option to return these reported emails to the user's inbox with the “No threats found” action? Because I don't see this option. In another tenant, under “Choose response Action,” I see “move or delete,” but the “inbox” option is grayed out. Why is that? Thank you very much!
