If your company runs on Microsoft 365—Exchange, Teams, and SharePoint—you have a massive attack surface. Most leaders assume Microsoft handles everything, but that is a dangerous bet. With the rise of remote work, personal devices, and an ever-evolving threat landscape, an improperly configured Office 365 environment is often the single biggest risk to your corporate data.

You are operating under the Shared Responsibility Model: Microsoft secures the cloud infrastructure, but you are responsible for securing the configuration, the identities, and the data stored within those applications. Ignoring this responsibility is betting your future on luck.

I’m Dan Duran, CTO of Rhyno Cybersecurity. We help growing organizations turn “we hope we’re secure” into “we know our exposure” by focusing on critical platforms like Microsoft 365.

The Microsoft 365 Security Audit Workflow

Most companies approach O365 security reactively: they wait for an incident, or they just run a basic, surface-level compliance check

Basically, you have two options:

• Non-Systematized Version: You check the easy settings, ignore the complexities of external SharePoint sharing, and allow default OAuth permissions that a hacker can easily exploit. You trust your data is protected until a remote laptop is stolen, an attacker gains control of user mailboxes, or a disgruntled employee leaks IP via Teams.
• Systematized Version: You run a comprehensive, repeatable audit that covers over 150 critical risk factors across your entire environment. Our methodology spans five stages—from Kick-off to Audit Execution to a final Certificate—ensuring you get a prioritized, actionable plan, not just a list of findings.

But let’s focus on what you can fix right now.

FIX These 3 EASY Fatal Settings

In every M365 environment we audit, we find simple configuration errors that provide an easy attack path. Here are three quick wins you can implement today that drastically reduce your risk:

1. Enforce MFA for All Admins

This sounds obvious, but many organizations stop at only enforcing Multi-Factor Authentication for Global Administrators. Attackers don’t just target Global Admins. They target Help Desk Admins, SharePoint Admins, or Exchange Admins—any role that has elevated permissions.

• The Fix: Use Conditional Access policies in Azure AD to mandate MFA for any administrative role, including the smaller, specialized ones. If you leave even one admin role unsecured, that’s your weakest link.

Bonus! Get Our Free Security Checklist

2. Disable Anonymous File Sharing in SharePoint/OneDrive

By default, M365 may allow users to create “Anyone with the link” sharing links. This setting is designed for convenience, but it is catastrophic for data control, as these links bypass all authentication.

• The Fix: Go to the SharePoint Admin Center and set the sharing policy to a maximum of “Existing guests” or “Specific people.” This ensures that every external access requires an email and authentication, giving you an audit trail and preventing sensitive data from living permanently outside your tenant.

Now, if you like these quick fixes, we’ve compiled a list of the most critical security gaps we find across both Microsoft and Google cloud environments. We put it into one easy-to-use guide.

Before you move on to the next tip, use the link below to download our Rapid Lock Security Checklist for Google and Microsoft. It’s a completely free resource that helps you audit your tenant in minutes.

3. Review and Deny High-Risk Third-Party App Access

Every time a user signs into an external tool (like a calendar scheduler or a new productivity app) and clicks “Accept,” they grant that app OAuth permissions to access your M365 data—sometimes even full mailbox access. This is a massive attack vector if the third-party app is compromised.

• The Fix: Go to the Azure AD Portal under Enterprise Applications. Review the list of third-party applications and filter by the permissions granted. Immediately disable or remove consent for any application that has access to sensitive scopes (like Mail.ReadWrite.All) and is either unused or untrusted.

These three fixes alone will put you ahead of 80% of organizations. But true, continuous security requires a holistic view. You need a process that checks the hundreds of complex, interacting policies across Exchange transport rules, Defender configuration, and Intune device settings.

If you’re serious about protecting your growth and need a comprehensive view of these 150+ risk factors—not just the easy ones—then it’s time for a proper, structured audit.

Reach out to us at Rhyno Cybersecurity. Use the “Contact Us” link in the description to book a conversation. We’ll help you move from hoping your configuration is secure to knowing your data is protected.