Jeremy Windmiller

Microsoft Security Matters Newsletter – October 2026 Edition

Hello everyone,

Welcome to the Microsoft Security Matters Newsletter – October 2026 Edition. Below is a curated roundup of Microsoft security updates, organized by topic to help you quickly find the news most relevant to your customers and conversations.

General

AI Security

Agent 365

  • The Microsoft AI and Agent Platform — Securing and Governing Intelligent Agents (2026-10-07, Microsoft Security Blog)
    In Part 1 , we explored the intelligence side of the Microsoft AI and Agent Platform: how agents understand work, reason over trusted context, use models and tools, and operate across experiences such as Microsoft 365 Copilot, Copilot Studio, Microsoft Foundry, Dynamics 365, GitHub, and custom appli

Azure Security & Defender for Cloud

  • Cloud Security Billing, Simplified: Introducing the Defender Workload Unit (2026-10-20, Microsoft Defender for Cloud Blog)
    That’s the thinking behind an upcoming improvement to Microsoft Defender for Cloud: the Defender Workload Unit , or DWU. It’s a new billing model and product experience that translates workload-specific usage into a common billing unit, with one unit price and one place to estimate and track costs.
  • Large OS Disk Encryption is now generally available for Azure Confidential VM migrations (2026-10-27, Microsoft Security Blog)
    Today, we are excited to announce the General Availability of Large OS Disk Encryption (LOSDE) for Azure Confidential VM migration scenarios. This capability removes a key adoption barrier for customers migrating sensitive workloads to Azure Confidential Virtual Machines by enabling encryption for o

Threat Intelligence

Microsoft Entra

  • What’s new in Microsoft Entra: October 2026 (2026-10-16, Microsoft Entra Blog)
    Over the last few months, I’ve spent a lot of time with customers and our teams on one of the biggest security shifts ahead of us: securing an enterprise where people and AI agents are both acting on behalf of the business. It’s a challenge shaping Microsoft’s approach to Secure AI. And while AI mak
  • Designing smarter access policies for hybrid enterprises (2026-10-22, Microsoft Entra Blog)
    Every hybrid enterprise eventually reaches the same point: the security model that worked when everyone was inside the corporate network no longer holds up when people, apps, and data are distributed across clouds, data centers, and unmanaged devices. Add AI agents acting on users’ behalf, and the i
  • Why identity needs network insight to make Zero Trust work (2026-10-27, Microsoft Entra Blog)
    Your users sign in successfully—and then what? The session can be hijacked, device posture can degrade, and traffic to non-federated SaaS and AI apps can slip past the identity controls you trust to protect them. That’s the gap admins see every day: identity tells you who, but not what’s happening a
  • AI agents are coming—are your identity controls prepared? (2026-10-30, Microsoft Entra Blog)
    AI is reshaping identity risk. Attackers now use AI to automate phishing, social engineering, and privilege escalation, making credential theft faster and more convincing than ever. SMS codes and push approvals can be intercepted, while standing privileges give attackers reach far beyond a single ac

Defender XDR & Sentinel

  • Introducing the Microsoft Sentinel ASIM EmailEvent schema (2026-10-07, Microsoft Sentinel Blog)
    Email remains one of the most common entry points for security threats. Yet email products often describe the same activity with different table names, fields, and values. This makes it harder to build detections and investigations that work consistently across data sources. The Microsoft Sentinel A
  • Secure Linux desktops with Microsoft Defender (2026-10-14, Microsoft Defender for Endpoint Blog)
    As more developers begin to use Linux desktops, they become more attractive to attackers: high-privilege, high-value, and easy for admins to overlook. A developer using Linux for day-to-day development may interact with source code repositories, continuous integration and continuous delivery (CI/CD)
  • Expanded cross-tenant delegated access in Microsoft Defender is generally available (2026-10-20, Microsoft Sentinel Blog)
    Security operations rarely stop at a single tenant boundary. Managed security service providers (MSSPs) protect many customer environments, and central security teams often operate across a tenant estate spanning business units, regions, or subsidiaries. In both cases, teams need to delegate securit
  • Manage all your Microsoft Sentinel data in one place with Unified Data Management (Public Preview) (2026-10-20, Microsoft Sentinel Blog)
    As security teams bring in more data from more sources and use it across SIEM and XDR workflows, decisions about connector health, ingestion volume, and cost optimization get harder. Today, we’re announcing the public preview of Unified Data Management for Microsoft Sentinel, available in the new Da
  • Turn threat intelligence into informed action with Microsoft Defender (2026-10-22, Microsoft Threat Protection Blog)
    Every new threat raises a familiar set of questions. Is it targeting our industry? Are we exposed? What should we investigate first? Answering those questions takes more than another feed or a longer list of indicators. It takes intelligence that brings the relevant context together and helps your t
  • Proofpoint’s Core Email Protection API solution joins the Microsoft Defender ICES vendor ecosystem (2026-10-26, Microsoft Defender for Office 365 Blog)
    Email remains the most exploited gateway for cyberattacks, as the threat landscape continues to get more sophisticated with attackers using AI to scale phishing, malware, and business email compromise. Microsoft Defender is a leading email security solution , helping organizations stay ahead of thes
  • Part 4: See, investigate, and measure email and collaboration attacks with Defender reporting (2026-10-27, Microsoft Defender for Office 365 Blog)
    Attacks rarely stay in one channel. A flood of spam email, a Teams chat from an unfamiliar organization, and a call from “the helpdesk” can all be part of the same attempt. Security teams need a unified way to see where attacks are happening across email and collaboration, investigate them quickly,
  • Growing our connector ecosystem with 500+ Microsoft Sentinel connectors (2026-10-28, Microsoft Sentinel Blog)
    Connecting the modern security environment Having spent years working across Microsoft’s cloud, AI, and customer-facing organizations. I have seen that technology delivers the greatest value when it works with the environments customers already operate. That’s especially true in cybersecurity. Most
  • Defending Linux in the age of AI-operated attacks (2026-10-29, Microsoft Defender for Endpoint Blog)
    Linux supports cloud services, containers, developer environments, business-critical applications, and a growing share of AI infrastructure. That makes Linux both essential to modern enterprises and increasingly attractive to attackers. AI is compressing the time required to research targets, vary p
  • Now generally available: Discover local AI agents with Microsoft Defender (2026-10-29, Microsoft Threat Protection Blog)
    As local agents have moved from experimentation into everyday work, traditional security visibility is no longer enough. Unlike static software, local agents such as coding assistants, command-line agents, desktop applications, and agentic development environments can operate on endpoints with acces
  • What’s new in Microsoft Sentinel: October 2026 (2026-10-30, Microsoft Sentinel Blog)
    Welcome back to What’s new in Microsoft Sentinel. In October, cross-tenant delegated access reaches general availability so you can run security operations across tenants with least privilege, the Advanced Security Information Model (ASIM) EmailEvent schema gives you one consistent structure for ema

Purview

  • Protecting Organizations from External Email Risks in Microsoft 365 Copilot (2026-10-08, Microsoft Security Blog)
    Introduction As organizations embrace Microsoft 365 Copilot (Copilot), a new category of risk emerges: what happens when Copilot grounds its responses in untrusted external emails? Messages from external or unverified senders can carry content Copilot shouldn’t rely on. A new policy in Microsoft Pur
  • Why DLP for External Web Search in Microsoft 365 Copilot Matters? (2026-10-08, Microsoft Security Blog)
    Introduction Microsoft 365 Copilot (Copilot) grounds its responses in your organizational data—emails, files, chats—and, optionally, the public web. With web search enabled, Copilot fetches real-time information from the Bing search service to deliver richer, more current answers. But what happens w

Learning