“`html

Microsoft 365 comes packed with powerful security tools — but most of them aren’t turned on by default. Out of the box, your organization may be far more exposed than you realize. After 31 years of working with small and mid-sized businesses across Nebraska and beyond, we’ve seen firsthand how a few missed configuration settings can leave the door wide open for phishing attacks, account takeovers, and data breaches. The good news? Most of these protections take minutes to enable and make an enormous difference.

Enable Multi-Factor Authentication (MFA) for Every User

This one isn’t optional anymore. MFA is the single most effective control you can implement to prevent unauthorized account access. Microsoft reports that MFA blocks over 99.9% of automated account compromise attacks. Yet many organizations still have users — often executives or long-tenured employees — who’ve been exempted “just for now.”

Start by enabling Security Defaults in Azure AD if your organization doesn’t have a more advanced licensing tier. If you have Azure AD Premium P1 or P2 (included in Microsoft 365 Business Premium), use Conditional Access policies instead — they give you far more granular control, such as requiring MFA only when users sign in from outside your network or from unmanaged devices.

Configure Microsoft Defender for Office 365

Defender for Office 365 goes well beyond basic spam filtering. If your licensing includes it (Plan 1 is included in Microsoft 365 Business Premium), make sure these features are actively configured:

  • Safe Links: Rewrites URLs in emails and Office documents and checks them in real time when clicked — catching malicious links even after they’ve been delivered.
  • Safe Attachments: Opens attachments in a sandbox environment before delivering them to users, blocking malware that bypasses signature-based detection.
  • Anti-Phishing Policies: Enable impersonation protection for your key executives and your domain. This catches spoofed emails that mimic your leadership team — one of the most common business email compromise tactics.

Don’t just enable these features — review the reports regularly. Defender produces detailed threat data that can reveal targeted attack patterns against your organization.

Audit and Restrict Mailbox Forwarding Rules

Attackers who gain access to a compromised mailbox often set up silent forwarding rules to an external address — sometimes collecting intelligence for months before anyone notices. Admins should audit existing forwarding rules across all mailboxes and, critically, block users from forwarding email externally by default unless there’s a documented business need.

In the Exchange Admin Center, create a mail flow rule that blocks automatic external forwarding. You can still allow exceptions on a case-by-case basis while preventing the most common post-breach data exfiltration technique we see in incident response situations.

Review and Tighten App Permissions

Users can grant third-party applications access to their Microsoft 365 data — calendars, email, files — without IT’s knowledge. Some of these apps are legitimate productivity tools; others are a serious liability. In Azure AD under Enterprise Applications, review what’s been authorized in your environment. Disable user consent for app registrations, or limit it to verified publishers only, and require admin approval for new integrations. This small policy change eliminates an entire category of OAuth-based phishing attacks.

Enable Unified Audit Logging

You cannot investigate what you didn’t log. Unified Audit Logging in Microsoft 365 captures user and admin activity across Exchange, SharePoint, Teams, and Azure AD. Surprisingly, it’s not always enabled by default on older tenants. Verify it’s active in the Microsoft Purview compliance portal.

At minimum, configure alerts for high-risk events: mass file downloads, changes to MFA settings, new admin role assignments, and logins from unusual geographic locations. These alerts won’t prevent an incident, but they dramatically reduce your detection and response time.

Implement a Privileged Access Strategy

Global Administrator is the most powerful role in your Microsoft 365 environment — and it should rarely be used. Assign granular admin roles (Exchange Admin, User Admin, Security Reader) instead of defaulting to Global Admin for every IT task. Require dedicated cloud-only admin accounts that are separate from day-to-day user accounts, and ensure those accounts are protected with MFA and monitored closely. Consider enabling Privileged Identity Management (PIM) if you have Azure AD P2 licensing — it provides just-in-time admin access with approval workflows and full audit trails.

Don’t Set It and Forget It

Microsoft 365 security isn’t a one-time project — it’s an ongoing discipline. Licensing tiers change, new features roll out, users get added, and threat actors adapt their tactics. A quarterly review of your security configurations, combined with regular end-user training, will keep your defenses strong as your business evolves.

If you’re unsure where your Microsoft 365 tenant stands today, Tier3 MSP can conduct a thorough security assessment and help you build a configuration that matches your risk profile and compliance requirements. We’ve been helping Nebraska businesses and MSPs nationwide strengthen their Microsoft environments for nearly three decades. Reach out to our team to start the conversation — no pressure, just practical guidance from people who do this every day.

“`