Microsoft Defender for Office 365 is email and collaboration security for Microsoft 365. It helps protect email, Microsoft Teams, SharePoint, and OneDrive against phishing, business email compromise (BEC), ransomware, and malicious links and attachments. It combines AI-powered detection, automated response, and reporting in one place, so you do not need a separate email security product. It comes in two plans: Plan 1 for prevention and detection, and Plan 2 for everything in Plan 1 plus threat hunting, XDR capabilities, and attack simulation training. It’s also available as part of select Microsoft 365 suite offerings.

Microsoft Defender for Office Plan 1 covers prevention and detection: protection across email, Microsoft Teams, SharePoint, and OneDrive, real-time protection for malicious links and QR codes, protection against zero-day malware in attachments, language model-based sentiment analysis, protection for internal email, and real-time reporting. Microsoft Defender for Office Plan 2 includes everything in Plan 1 and adds advanced threat hunting, automated investigation and response, attack simulation training, cyberthreat campaign tracking, and cross-domain XDR. If someone on your team or your IT partner investigates incidents, Plan 2 gives them the tools to do it. See Plans and pricing above for a side-by-side view.

BEC attacks impersonate someone your team trusts—an executive, a supplier, a colleague—and ask for a payment or a password. There is usually no malware to detect. Defender for Office 365 reads intent rather than attachments, using built-in large language models to detect attacker intent, then disrupts the attack automatically by disabling compromised users, isolating compromised devices, and removing malicious mail after delivery. 

It checks every message before it reaches your team. Defender for Office 365 uses AI and sentiment analysis to read the intent behind a message, detonates links and attachments in a safe environment, and blocks malicious links and QR codes in real time. If something slips through, post-delivery removal pulls it back out of the inbox. Attack simulation training in Plan 2 helps your team recognize the next attempt. Most of this runs automatically, which matters if you have limited resources.

Small businesses need protection beyond standard spam filtering. Spam filters catch bulk junk and known bad senders, but they’re less effective against targeted attacks with no malware, including AI-driven phishing, business email compromise, and QR code scams that convince a person to act. Defender for Office 365 Plan 1 adds core prevention and detection across email, Teams, SharePoint, and OneDrive, including safe links, attachment detonation, anti-spoofing checks, and reporting. Plan 2 adds attack simulation training, threat hunting, automated investigation, and response.

Cybersecurity costs vary based on business size, risk, and the level of protection needed. Defender for Office 365 helps manage cost by adding email and collaboration security to Microsoft 365, including phishing protection, safe links, and thread detection. Plan 1 covers core prevention and detection. Plan 2 adds advanced investigation, XDR capabilities, and attack simulation training. See plans and pricing to compare options.