Microsoft 365 Security Checklist for Small Businesses Bothell, Washington
Microsoft 365 Security Checklist for Small Businesses
Microsoft 365 is where many businesses run their daily work.
Email, calendars, Teams messages, SharePoint files, OneDrive documents, user accounts, and business communication all live inside Microsoft 365.
That makes it one of the most important systems your company uses.
It also makes it one of the biggest security targets.
Many businesses assume Microsoft 365 is secure by default. Microsoft provides the platform, but your business is still responsible for how users, permissions, sharing, devices, and security settings are configured.
Here is a practical Microsoft 365 security checklist for small and midsize businesses.
1. Require Multi-Factor Authentication
Every user should have multi-factor authentication enabled.
MFA helps protect accounts even if a password is stolen. This is especially important for email because email accounts are often used to reset passwords for other services.
MFA should be required for:
- All employees
- Admin accounts
- Finance users
- Leadership
- Remote users
- Users with access to sensitive data
Do not leave MFA optional.
2. Protect Administrator Accounts
Administrator accounts need extra protection.
Not every user should be a global administrator. In fact, very few people should have that level of access.
Review all admin roles and remove unnecessary permissions.
Admin accounts should have strong MFA, separate credentials, and limited use. They should not be used for normal daily email and browsing.
3. Review Sign-In Activity
Microsoft 365 sign-in logs can show suspicious activity.
Look for:
- Sign-ins from unusual countries
- Repeated failed login attempts
- Legacy authentication attempts
- Sign-ins from unfamiliar devices
- Impossible travel activity
- Risky user alerts
These logs can help identify compromised accounts early.
4. Block Legacy Authentication
Older authentication methods can create security risk because they may not support MFA properly.
Blocking legacy authentication is an important Microsoft 365 hardening step.
This can help reduce exposure from older email clients, outdated apps, and insecure sign-in methods.
5. Review SharePoint and OneDrive Sharing
SharePoint and OneDrive make file sharing easy, but they can also create risk when sharing is too open.
Review:
- Anonymous links
- External sharing permissions
- Guest users
- Link expiration settings
- Sensitive folders
- Who can share externally
- Whether users can share with anyone
Your business should make collaboration easy without exposing sensitive data.
6. Check Mail Forwarding Rules
Attackers often create forwarding rules after compromising email accounts.
Review user mailboxes for forwarding rules that send messages outside the company.
Also review mailbox rules that delete, hide, or move emails unexpectedly.
This is especially important for finance, leadership, and customer-facing accounts.
7. Secure Email Against Phishing
Email is one of the most common attack paths.
Your business should have protections against phishing, spoofing, malicious attachments, suspicious links, and impersonation.
Employees should also know how to report suspicious emails quickly.
Technology helps, but user awareness still matters.
8. Review User Offboarding
When an employee leaves, their access should be removed quickly and completely.
A proper offboarding process should include:
- Blocking sign-in
- Resetting the password
- Removing MFA devices
- Recovering company devices
- Converting or preserving the mailbox if needed
- Removing SharePoint and OneDrive access
- Removing access to third-party apps
Offboarding is one of the most overlooked Microsoft 365 security risks.
9. Review Microsoft 365 Licenses
Unused licenses cost money. Unused accounts create security risk.
Review active users, assigned licenses, shared mailboxes, disabled users, and old accounts.
This helps clean up both cost and security.
10. Back Up Microsoft 365 Data
Microsoft 365 provides cloud infrastructure, but your business still needs a plan for data recovery.
Accidental deletion, ransomware, malicious activity, and retention gaps can still create problems.
Review how your email, SharePoint, OneDrive, and Teams data are protected.
How MTech Helps
MTech helps businesses manage and secure Microsoft 365.
We can review MFA, admin roles, sharing settings, sign-in logs, email security, user accounts, offboarding, backups, and licensing.
The goal is simple: help your team use Microsoft 365 safely without making daily work harder than it needs to be.
Final Thoughts
Microsoft 365 is powerful, but it needs to be managed properly.
Small configuration gaps can create major security risks.
If your company is not sure whether Microsoft 365 is configured securely, MTech can help review your environment and prioritize the most important fixes.