Microsoft Defender for Office 365 is the Microsoft 365 solution designed to protect users from threats delivered through email and collaboration workloads. SCI training material explains that Defender for Office 365 protects Exchange Online, Microsoft Teams, SharePoint Online, and OneDrive for Business by detecting and blocking malware, phishing, and other advanced attacks that use messages and shared content as the delivery channel.

A key capability is Safe Links, which specifically protects against malicious URLs. When a user receives an email, Teams chat message, or channel post that contains a hyperlink, Safe Links scans and rewrites that URL. At the moment the user clicks, the link is checked again; if it is identified as malicious or leads to a known phishing or malware-hosting site, access is blocked and a warning page is shown. This time-of-click protection is emphasized in Microsoft’s security documentation as a primary defense against weaponized links in email and collaborative communications.

By comparison, Microsoft Defender for Identity focuses on detecting identity-related threats in on-premises Active Directory, Defender for Endpoint protects devices and endpoints, and Defender for Cloud Apps secures SaaS applications and shadow IT. None of these are the primary solution for blocking malicious links in email, chats, and channels. Therefore, the correct choice is Microsoft Defender for Office 365.