Pass SC-900 Exam Guide

In Microsoft Defender for Endpoint, attack surface reduction (ASR) is described as the first defensive layer in the protection stack, and Network protection is a core ASR capability. Microsoft’s documentation states that “Attack surface reduction provides the first line of defense in the stack.” It further explains that these capabilities are designed to reduce opportunities for compromise before malware can run or persistence can be established. Within ASR, Microsoft specifically defines Network protection as a feature that “helps reduce the attack surface of your devices from Internet-based events.” Microsoft also clarifies how it works: “It prevents employees from using any application to access dangerous domains that may host phishing scams, exploits, and other malicious content on the Internet.”

Because the question asks for the feature in Defender for Endpoint that delivers the first line of defense by reducing the attack surface, the applicable ASR capability is Network protection. It proactively blocks access to known malicious IPs, domains, and URLs, shrinking the exploitable surface area and thereby reducing risk before an attack can execute. By contrast, automated investigation and automated remediation act after detections to contain and fix issues, and advanced hunting is an analyst-driven, query-based detection and investigation tool—not an attack-surface–reduction control. Hence, Network protection is the correct choice.

eDiscovery

In Microsoft Purview, eDiscovery is the purpose-built compliance solution for legal and investigative workflows. Microsoft’s SCI materials describe eDiscovery as the tool that enables organizations to identify, preserve/hold, collect, review, and export potentially relevant content across Microsoft 365 services. Official guidance explains that eDiscovery (Standard) “provides search, hold, and export capabilities” for content in Exchange, SharePoint, OneDrive, Teams, and more. Another description states that eDiscovery (Premium) helps you “identify, preserve, collect, review, analyze, and export content” for legal matters and internal investigations. These capabilities are designed to support the eDiscovery lifecycle by allowing admins and case managers to: create cases, define custodians and non-custodial data sources, run targeted searches, apply legal holds to prevent data alteration or deletion, perform review and analytics, and export responsive data packages for counsel or regulators.

By contrast, Data Loss Prevention (DLP) protects sensitive information from accidental or inappropriate sharing; Customer Lockbox governs Microsoft engineer access to your data for support; and resource locks protect Azure resources from accidental deletion or modification. Therefore, the Microsoft SCI control that is explicitly used to identify, hold, and export electronic information for an investigation is Microsoft Purview eDiscovery.

Microsoft describes hybrid identity as integrating on-premises Active Directory with Microsoft Entra ID (Azure AD) so that “your on-premises identities are synchronized to Azure AD” for a single identity across cloud and on-prem apps. In this model, directory objects (users, groups, and selected attributes) flow from on-premises AD to Azure AD using Azure AD Connect or Cloud Sync; this is the canonical direction for provisioning in hybrid environments. Microsoft further explains that while certain writeback features (such as password writeback, device or group writeback scenarios) are supported, cloud-created users do not automatically sync down to on-premises AD; account provisioning remains authoritative on-prem unless you deploy specific, limited writeback features—there is no default “user account creation from Azure AD to AD DS.” For authentication, Microsoft states that hybrid identity supports cloud authentication (Password Hash Synchronization or Pass-through Authentication) where Azure AD performs the sign-in, or federation with another identity provider (e.g., AD FS or a third-party IdP) where that provider validates credentials and issues tokens to Azure AD. These statements align with Microsoft’s SCI guidance on hybrid identity: on-prem to cloud sync is standard; automatic reverse user sync is not; and authentication can be handled by Azure AD or a federated IdP depending on the chosen sign-in method.

Microsoft 365 Information Barriers are compliance policies used “to prevent certain segments of users from communicating or collaborating with each other.” In Microsoft’s guidance, IB policies are designed for scenarios like insider trading restrictions, M&A deal rooms, or research–sales separation, where it’s necessary to block chats, calls, and collaboration between defined user segments. The documentation explains that when IB policies are in place, “users in the blocked segments cannot search, discover, or communicate with each other in Microsoft Teams,” and IB v2 extends these controls to additional collaboration workloads such as SharePoint and OneDrive. By contrast, email restrictions in Exchange Online are addressed through mail flow rules or other Exchange features, not information barriers, and restricting unauthenticated access or external sharing is handled by identity access controls and sharing settings, not IB. Therefore, the specific use case is restricting Microsoft Teams chats (and related collaboration) between certain groups within an organization.