Safeguarding Microsoft Teams with Microsoft Defender for Office 365
As organizations rely more on Microsoft Teams for daily collaboration, securing this platform has become a top priority. Threat actors are increasingly targeting Teams chats and channels with phishing links and malicious files, making it critical for IT admins and security professionals to extend protection beyond email. Enter Microsoft Defender for Office 365, now armed with dedicated Teams protection capabilities. Microsoft Defender for Office 365 enables users to report suspicious messages, brings time-of-click scanning of URLs and files into Teams conversations, and provides rich alerts and hunting insights for SecOps teams. As a collaborative piece between Pierre Thoor, a Microsoft Security Most Valuable Professional (MVP), and the Defender for Office 365 Product Engineering Team, the below guides with accompanying videos emphasize a proactive, user-driven approach to threat detection and response, turning everyday Teams interactions into actionable security signals for SecOps. See something, say something: Reporting suspicious messages in Microsoft Teams Your fastest sensor isn’t AI – it’s your people. Report this message in Microsoft Teams lets anyone flag a suspicious conversation in two clicks and routes a triageable submission to your security team in the Microsoft Defender portal. Why this matters: Speed to signal: Catch threats at the conversation layer, not just in email. Complete context: Original message, participants, URLs, and verdicts in one place. Habit-forming: A simple, repeatable action employees remember under pressure. How to report (desktop, web, and mobile) In Desktop/Web Hover the message → … More options → Report this message Select Security concern → (optional) add a short note → Report In Mobile (iOS/Android) app Long-press the message → Report message Select Security concern → (optional) add a short note → Report *Tip: Short notes like “Unexpected MFA reset link” help analysts triage faster. Where reports go (for security teams) In the Microsoft Defender portal, navigate to: Investigation & response → Actions and submissions → Submissions → User reported. Open an item to view the Teams message entity (sender/domain, Teams message ID, extracted URLs, verdict) and take action – mark as phish/clean, pivot to Explorer or Advanced Hunting, or copy indicators. Quick setup check Defender portal → Settings → Email & collaboration → User reported settings: enable Monitor reported messages in Microsoft Teams. Licensing: Microsoft Defender for Office 365 Plan 2 (included in Microsoft 365 E5). What good looks like (mini playbook) User reports the message. Security triages the submission and captures the URL/domain and other indicators. Block or allow as appropriate via the Tenant Allow/Block List (TABL). Hunt for related activity or clicks (see Video 3). Close the loop: thank the reporter and share the outcome to reinforce the behavior. Common gotchas Reporting is disabled in the Teams messaging policy – verify before rollout. Some users assume “Report” notifies the sender – clarify that it routes to the Security team, not the sender. Call to action: Enable reporting for your users and add this line to your awareness site: “If it feels phishy, report – don’t click.” Think before you click - Safe Links catches threats at click-time Links can change after delivery. Safe Links waits until click-time, evaluates the destination, and shows an in-app warning page in Teams. Pair it with the Tenant Allow/Block List (TABL) to tune quickly across the tenant. Why this matters Prevents delayed redirects: Avoids “clean-at-send” methods. Consistent protection in Teams: Familiar warning UX reduces risky clicks. Rapid tuning: Block newly observed domains in seconds; no advanced transport rules required. What you’ll see in the video Policy check (Teams in scope) Defender portal → Email & collaboration → Policies & rules → Threat policies → Safe Links → ensure Apply Safe Links to Microsoft Teams is enabled for target users or groups OR that you use Standard/Strict Preset Policy. Warning page at click-time Post a benign test URL in Teams and click it to show the Safe Links warning experience. Block it as you spot it (Allow/Block) Defender portal → Threat policies → Tenant Allow/Block List → URLs → Add (domain or URL). Re-click in Teams – now blocked at click-time. Optional telemetry (Advanced Hunting) Confirm outcomes and adoption: UrlClickEvents | where Timestamp > ago(24h) and Workload == "Teams" | summarize Clicks=count(), Users=dcount(AccountUpn) by ActionType | order by Clicks desc Deployment tips Start with a pilot group that includes IT + power users; expand after validation. Create a review cadence for TABL (e.g., monthly) and expire temporary blocks. Troubleshooting No warning page? Verify policy scope includes the user and the Teams workload. Block not taking effect? Give TABL a short sync window, then re-test; confirm you blocked the correct domain/URL pattern. “Hunt the chat”: Advanced hunting for Teams threats Overview With Advanced Hunting you can quickly reconstruct activity in Microsoft Teams – who sent the message, who clicked the link, and what protections kicked in. This section shows how the four Teams-relevant tables work together, so you can move from signal to action quickly. New: message warnings for malicious URLs (internal and external) Teams now shows a warning banner on messages that contain URLs flagged as spam, phishing, or malware. Warnings appear in internal and external chats/channels, and can be added after delivery (up to ~48 hours) if a URL’s reputation changes. This complements Safe Links (time-of-click) and doesn’t replace ZAP; when ZAP removes a message, that action takes precedence. Public preview began September 2025; GA November 2025, enabled by default at GA and manageable in Teams admin center → Messaging settings. See Message Center: https://admin.cloud.microsoft/?#/MessageCenter/:/messages/MC1150984 The four tables you’ll use MessageEvents – delivery context (sender, thread, internal vs. external). MessagePostDeliveryEvents – post-delivery actions, including Phish ZAP and Malware ZAP. MessageUrlInfo – URLs extracted from Teams messages. UrlClickEvents – time-of-click outcomes for links, including those clicked in Teams. What you’ll learn in the video Surface active external domains in your tenant’s Teams chats. Identify who clicked risky links and the click outcomes (via Safe Links telemetry). See where message warnings appear in the chat UI. Pivot to an incident and block indicators fast via the Tenant Allow/Block List (TABL). A couple hunts to try right now 1) Malicious verdicts in Teams (last 24 hours) Find messages that already carry a Spam/Phish/Malware verdict – your fastest triage queue. MessageEvents | where Timestamp > ago(1d) | where ThreatTypes has "Phish" or ThreatTypes has "Malware" or ThreatTypes has "Spam" | project Timestamp, SenderDisplayName, SenderEmailAddress, RecipientDetails, IsOwnedThread, ThreadType, IsExternalThread, ReportId Use it for: a quick sweep + pivot to incident/entities, then TABL block if needed. 2) “IT helpdesk” imposters in external DMs (last 5 days) Surface social-engineering lures that impersonate support. MessageEvents | where Timestamp > ago(5d) | where IsExternalThread == true | where (RecipientDetails has "help" and RecipientDetails has "desk") or (RecipientDetails has "it" and RecipientDetails has "support") or (RecipientDetails has "working" and RecipientDetails has "home") or (SenderDisplayName has "help" and SenderDisplayName has "desk") or (SenderDisplayName has "it" and SenderDisplayName has "support") or (SenderDisplayName has "working" and SenderDisplayName has "home") | project Timestamp, SenderDisplayName, SenderEmailAddress, RecipientDetails, IsOwnedThread, ThreadType, ReportId Use it for: first-contact scams (external tenant posing as IT). Pair with Safe Links telemetry to see who clicked. Tip: has is token-aware and generally faster/cleaner than contains for word matches. Keep both hunts detection-ready by ensuring the final projection includes Timestamp and ReportId. 3) BONUS! External DMs with links (last 7 days) MessageEvents | where Timestamp > ago(7d) and IsExternalThread == true | join kind=inner (MessageUrlInfo) on TeamsMessageId | summarize Links=dcount(Url), Senders=dcount(SenderEmailAddress) by UrlDomain | top 10 by Links desc 4) Who clicked (Teams workload) – exposure view: UrlClickEvents | where Timestamp > ago(7d) and Workload == "Teams" | project Timestamp, AccountUpn, Url, ActionType | order by Timestamp desc “From Hunt to Action”: Respond & contain Finding a risky link in Teams is only half the job. This walkthrough shows how to go from detection to containment – block the domain, clean up delivered messages, and cut attacker access. Why this matters Speed: Shrink time from “we saw it” to “it’s blocked”. Consistency: Turns ad-hoc hunting into a repeatable response flow. Coverage: Pair URL blocking with identity and device containment. What you’ll see in the video Turn a hunt into an alert In Advanced Hunting, run a short query (below) and choose Create detection rule to schedule it. Alerts auto-create incidents you can triage. Block at click-time (Safe Links + TABL) In the incident, open the URL entity and add the URL/domain to the Tenant Allow/Block List (TABL) so future Teams clicks are blocked by Safe Links. Post-delivery cleanup (ZAP) If a malicious message slipped through, ZAP can remove or mark it after delivery. You’ll see evidence on the incident timeline. Contain accounts and devices Revoke user sessions in Entra ID to invalidate active tokens. Reset the password (and require strong, unique credentials), then enforce MFA for the account. Review MFA methods and remove anything suspicious; review app consents and revoke illicit grants. If endpoints are onboarded, isolate the device in Microsoft Defender for Endpoint to stop outbound connections while you investigate. The Microsoft Learn guide, https://learn.microsoft.com/en-us/defender-office-365/responding-to-a-compromised-email-account, for compromised accounts recommends session revocation, password reset, MFA enforcement, reviewing OAuth app consents and admin roles, and checking mail forwarding/rules – steps that complement the Teams response you see here. The hunt This KQL surfaces rare external domains in Teams and any user clicks. let lookback = 1d; // External Teams messages let externalMsgs = MessageEvents | where Timestamp > ago(lookback) and IsExternalThread == true | project MsgTime = Timestamp, TeamsMessageId, SenderEmailAddress, ME_ReportId = ReportId; // URLs found in Teams messages let urlsInMsgs = MessageUrlInfo | where Timestamp > ago(lookback) | project MUI_Time = Timestamp, TeamsMessageId, Url, UrlDomain, MUI_ReportId = ReportId; // Clicks coming from Teams let clicks = UrlClickEvents | where Timestamp > ago(lookback) and Workload == "Teams" | project ClickTime = Timestamp, Url, Clicker = AccountUpn, ClickAction = ActionType, UCE_ReportId = ReportId; // Define “rare” domains in the period let rareDomains = urlsInMsgs | summarize msgCount = dcount(TeamsMessageId) by UrlDomain | where msgCount < 3; rareDomains | join kind=inner (urlsInMsgs) on UrlDomain | join kind=leftouter (externalMsgs) on TeamsMessageId | join kind=leftouter (clicks) on Url | project Timestamp = coalesce(ClickTime, MUI_Time, MsgTime), UrlDomain, Url, SenderEmailAddress, Clicker, ClickTime, ClickAction, TeamsMessageId, ReportId = coalesce(UCE_ReportId, MUI_ReportId, ME_ReportId) After verifying results, select Create detection rule, set a schedule (e.g., hourly), and map entities so incidents include the right artifacts. What good looks like (response playbook) Alert fires → open incident; confirm scope and entities. Block URL/domain via TABL to stop future clicks. Confirm ZAP removed or marked delivered messages. Revoke sessions and reset password; enforce MFA. Review MFA methods and remove unknown devices/methods. Audit app consents (revoke illicit grants) and verify the user holds no unexpected admin roles. If email abuse is suspected, check for forwarding or malicious Inbox rules. Isolate device if execution is suspected; collect artifacts and un-isolate after remediation. FAQs Does the block remove the message? No – TABL blocks at click-time. Post-delivery removal is handled by ZAP when detections apply. Will revoking sessions disrupt users? It forces sign-in again (expected). Communicate this in your response template. What if the attacker used consent phishing? Revoke the offending enterprise app consent and review publisher verification status. Call to action: Save the query, create the detection, and attach this playbook to your incident template. The goal every time: find → block → clean up → contain Securing Microsoft Teams is most effective when technology and people work together. By enabling user reporting, leveraging real-time protections, and empowering security teams to act quickly, organizations can turn everyday collaboration into a strong defense against threats. ## 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 – A Four-Part Guide to Secure Collaboration" 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, Pierre Thoor with support of the Microsoft Defender for Office 365 product team. Pierre Thoor Microsoft Security MVP | Microsoft Defender for Office 365 Champ Get Involved and Learn More Log in and follow this Microsoft Defender for Office 365 blog and follow/post in the Microsoft Defender for Office 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
Sentinel Data Connector: Google Workspace (G Suite) (using Azure Functions)
I'm encountering a problem when attempting to run the GWorkspace_Report workbook in Azure Sentinel. The query is throwing this error related to the union operator: 'union' operator: Failed to resolve table expression named 'GWorkspace_ReportsAPI_gcp_CL' I've double-checked, and the GoogleWorkspaceReports connector is installed and updated to version 3.0.2. Has anyone seen this or know what might be causing the table GWorkspace_ReportsAPI_gcp_CL to be unresolved? Thanks!Introducing the Microsoft Defender for Office 365 ICES vendor ecosystem
In today's digital landscape, the need for comprehensive security measures is more critical than ever, as email continues to be a primary vector for cyberattacks such as phishing and malware. To address this, Microsoft Defender for Office 365 leverages the extensive scale of Microsoft's threat intelligence, which processes trillions of signals daily. By integrating Large Language Models (LLMs) and advanced Natural Language Processing, Defender for Office 365 empowers organizations with AI-driven threat detection, behavioral analytics, and automated responses thus proactively identifying and neutralizing risks before they reach end users. This collaborative defense approach reinforces the principle that security is a team sport, requiring shared intelligence and coordinated action across the ecosystem. We recognize in today’s dynamic cyber threat landscape, defense-in-depth strategy has become a vital approach not only for Microsoft customers but also across the broader Secure Email Gateway (SEG) market. Organizations are increasingly adopting layered security solutions to comply with regulatory requirements, enhanced detection, and ensure robust protection. To address this, we’re announcing the Microsoft Defender for Office 365 ICES Vendor Ecosystem — a unified framework that enables seamless integration with trusted third-party vendors. This ecosystem is designed to eliminate integration friction and deliver: Broader detection coverage through vendor diversity Transparency across Microsoft Defender for Office 365 and partner detections Streamlined SOC workflows through consistent policy enforcement and shared investigation tools Stronger compliance alignment with layered security mandates This partner ecosystem is about creating a cohesive defense fabric that enhances SOC efficiency with Microsoft Defender for Office 365 as the foundation. The ecosystem also provides flexibility, scalability, and preparedness for the complexities of contemporary enterprise security. With this in mind, we are pleased to announce that our trusted ICES security vendors, Darktrace and KnowBe4, have become the first launch partners within our ecosystem. They offer customers a seamless and collaborative defense framework where each solution enhances the strengths of the others. We welcome additional partners soon as we continue to expand this integrated ecosystem. “Our integration with Microsoft gives security teams the tools they need to act faster and more precisely to detect and respond to threats,” said Jill Popelka, CEO of Darktrace. “Together, we’re strengthening defenses where it matters most to our customers —at the inbox.” “I’m incredibly excited at the opportunity afforded by this partnership with Microsoft and the deeper integrations it enables. Leveraging this integration allows us to use our vast quorum of data around email security and human risk in a way that provides the most comprehensive layered security approach available to the market. A complementary defense strategy is mandatory and this integration with Microsoft M365 furthers that vision by combining our capabilities to create comprehensive defense strategies that address the full spectrum of modern cyber threats.” noted Greg Kras, Chief Product Officer @ KnowBe4 Unified Quarantine The core strength of this new ecosystem is the seamless integration between Defender for Office 365 and its ICES partners, through the Unified Quarantine feature. Managing quarantined messages from multiple solutions can often be complex and inefficient. Unified Quarantine streamlines the process by consolidating quarantined items identified by both Defender for Office 365 and third-party (3P) solutions into a single, unified interface, enhancing customer ease and visibility. Administrators can efficiently review, release, or remediate messages through this unified interface, irrespective of the provider that identified the threat. This approach not only optimizes time management but also guarantees uniform policy enforcement and facilitates transparency on detections, resulting in improved operational efficiency and a more coherent user experience. As part of the Unified Quarantine, security admins can also see which provider quarantined the message. Transparency and Insight Across Solutions In environments with multiple email security solutions, transparency is crucial to understanding each vendor's detections. Microsoft Defender for Office 365 offers a unified dashboard that clearly distinguishes between threats stopped by Defender and those identified by third-party solutions, ensuring transparent and fair attribution of protection value. This dashboard provides security teams with a comprehensive view of how each solution contributes to protection, helping to identify overlapping coverage and areas of unique value. This clarity supports more informed decision-making around threat trends, policy optimization, and vendor strategy fostering stronger collaboration between internal teams and external partners. Deeper SOC Investigation Capabilities: Threat Explorer, Advanced Hunting, and Email Entity Page Modern defenders need tools for rapid investigation, root cause analysis, and tactical response. The Defender for Office 365 ecosystem unifies investigative workflows across partner solutions. Within Threat Explorer, security analysts can seamlessly pivot between messages actioned by Microsoft Defender for Office 365 and those flagged by integrated partners. The side-by-side display of verdicts and actions enables quick correlation and pattern recognition. Advanced Hunting brings even greater depth, allowing analysts to craft queries that span both Microsoft Defender for Office 365S and 3P data sources. This holistic view accelerates threat hunting and helps organizations surface novel attack techniques or gaps in coverage. EmailEvents | where Timestamp > ago(7d) //List emails caught by a Third-party solution | where DetectionMethods contains "Thirdparty" | project NetworkMessageId, RecipientEmailAddress, ThreatTypes, DetectionMethods, AdditionalFields, LatestDeliveryLocation On the Email Entity Page, every message surfaces a complete action history, including which product took action and what verdict was assigned. This granular visibility demystifies complex incidents and builds confidence in the layered defense model. Summary As the threat landscape continues to evolve, so must our defenses. While organizations embrace defense-in-depth, fragmented integrations may lead to unintended consequences such as diminished detection capabilities, overlapping controls, and SOC inefficiencies. With the Defender for Office 365 ICES vendor ecosystem, Microsoft is setting a new standard for collaborative, integrated security platforms. By combining proven protection, seamless partnerships, and unified visibility, organizations can embrace defense-in-depth without complexity or compromise. Whether combating phishing, malware, or the next generation of email-borne threats, customers benefit from a defense-in-depth strategy built for agility and efficiency. With hands-off enablement, unified experiences, and unmatched transparency, the Defender for Office 365 ecosystem empowers every organization to stay one step ahead—today and tomorrow. Learn More To learn more about the Microsoft Defender for Office 365 ICES Vendor Ecosystem, please visit https://learn.microsoft.com/defender-office-365/mdo-ices-vendor-ecosystem.
Help me understand why this email was quarantined?
I'm pretty familiar with Defender's Threat Policies. I've probably set them up on 40 tenants. I know the Hosted Content Filter Policy is backend for Anti Spam Inbound policy. I know that, confusingly, the AntiSpam Inbound Policies contain the actions for High Confidence/Normal Confidence Phishing - NOT the AntiPhishing policies (which seem more geared towards impersonation). What I DON'T know is why this was quarantined - and whether the anti-phish policy had anything to do with it. The Policy Type linked is the IB Anti Spam. This tenant is one of the few we have set at a BCL tolerance level of 7 - which shows me that 0 messages in the last 60 days would've been caught for this reason (which would include the email in question). So it was either the SCL or some 'anti phish' component of the anti-spam policy. I have none of the custom 'increase spam score' markers here. I was sure there was a 'evidence' tab within email entity, but i guess not - the only info I have about the detection (now released) is the following: This particular sender does not send reliably over 45 days, but also has been a business partner of this tenant for decades. So rather than the Tenant Allow/Block list which allows a max of 45 days, I want to add it to the offending policy. which SEEMS like it would be the inbound anti-spam - except that it also says it's phishing everywhere. I don't want to bypass both the phishing and spam policies unless I have to - but I don't really know why this got blocked. It's an external address that had sent an email days ago that got through without issue... This one has an attached pdf, but so do they all. Thoughts?Protect your organizations against QR code phishing with Defender for Office 365
QR code phishing campaigns have most recently become the fastest growing type of email-based attack. These types of attacks are growing and embed QR code images linked to malicious content directly into the email body, to evade detection. They often entice unwitting users with seemingly genuine prompts, like a password reset or a two-factor authentication request. Microsoft Defender for Office 365 is continuously adapting as threat actors evolve their methodologies. In this blog post we’ll share more details on how we’re helping defenders address this threat and keeping end-users safe.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!'system has learned from the submission / mail is automatically allowed'
Hey folks, got an alert about a tenant allow//block list entry expiring. Only recently did we start getting these, because only recently did we start using expiring whitelisting. But I'm a little confused by the details, which says 'Mail from x is now automatically alllowed and the allow entry has been removed' and the activity that ''an allow entry is no longer required as the system has learned from the submission' The referenced email is actually an internal tenant - it receives ticket requests, and sends out ticket updates. But I'm REALLY curious about the 'automatic' allowing. Is this a feature limited to Defender 2, or part of Microsoft's AI detection framework for all 365 Defender/EOP? I don't even remember submitting this email - if I did, it was probably more than 45 days ago. So 1) Is this notice primarily that the entry had expired, but ALSO it's not needed or does this send out as soon as 'the system' recognizes it as legitimate, and removed regardless of the time left? 2) is there a way to review a list of entries Microsoft has 'accepted'? 3) What exactly does this 'allow'? I know that the tenant allow/block list allowed a certain set of lower-risk indicators in an email, but still blocked some higher-risk ones - unless there was a submission made. At that point, more is allowed. But there's still a limit, compared to a blanket bypass on the policy itself.
