5 Microsoft 365 Security Tips Every Small Business Should Follow

Microsoft 365 gives small businesses convenient access to email, cloud storage, file sharing, calendars, and collaboration tools. However, keeping these services secure requires more than simply purchasing a Microsoft 365 subscription.

A compromised Microsoft 365 account may allow a cybercriminal to read company emails, impersonate an employee, access files in OneDrive or SharePoint, and send convincing phishing messages to customers and vendors.

The good news is that businesses do not need an enterprise-sized security team to reduce these risks. By following a few essential Microsoft 365 security best practices, small businesses can make their accounts significantly harder to compromise.

Here are five things every small business should do to protect its Microsoft 365 accounts.

1. Require Multi-Factor Authentication for Every User

Passwords alone are no longer enough to protect business accounts. They can be stolen through phishing emails, reused across multiple websites, exposed in data breaches, or guessed using automated tools.

Multi-factor authentication, or MFA, requires users to provide an additional form of verification when signing in. This may include an approval through the Microsoft Authenticator app, a security key, a passkey, or another approved authentication method.

Even if an attacker obtains an employee’s password, MFA creates another barrier that can prevent the attacker from accessing the account.

MFA should be required for:

• Employees
• Managers and executives
• Contractors
• Temporary users
• IT administrators
• Any third party with access to company systems

Microsoft provides security defaults that can help smaller organizations establish baseline identity protection. Businesses using Microsoft 365 Business Premium can also use Conditional Access policies to apply more detailed rules.

For example, Conditional Access can block or challenge sign-ins based on the user’s location, device security status, role, or level of risk.

MFA should be enabled across the entire organization. Protecting only administrators or selected employees leaves other accounts vulnerable.

2. Secure Administrator Accounts and Limit User Access

Administrator accounts can change security settings, create users, access sensitive information, and control important parts of the Microsoft 365 environment. If one of these accounts is compromised, the consequences can affect the entire business.

Employees should receive only the access they need to perform their jobs. This approach is known as the principle of least privilege.

To reduce unnecessary access:

• Limit the number of users with administrator privileges.
• Give employees the minimum permissions required for their roles.
• Avoid using shared user or administrator accounts.
• Use separate accounts for everyday work and administrative tasks.
• Remove access promptly when an employee or contractor leaves.
• Review user permissions regularly.
• Disable old, inactive, or unused accounts.

Businesses should also maintain at least one protected emergency administrator account that can be used if normal administrative access becomes unavailable. Access to this account should be tightly controlled and monitored.

User access management is not a one-time task. Permissions that were appropriate when an employee joined the company may no longer be suitable after a role change or departure.

A scheduled access review helps prevent old accounts and excessive permissions from becoming security weaknesses.

3. Strengthen Email and Phishing Protection

Email remains one of the most common entry points for cyberattacks. A phishing message may attempt to steal a password, convince an employee to open a malicious attachment, or trick someone into changing payment information.

A successful email compromise can extend beyond the mailbox. Depending on the user’s permissions, an attacker may also gain access to contacts, calendars, OneDrive files, SharePoint documents, and other connected Microsoft 365 services.

Small businesses should use Microsoft 365’s available email protections, including:

• Anti-phishing policies
• Anti-spam and anti-malware filtering
• Impersonation protection
• Safe Links
• Safe Attachments
• Alerts for suspicious account activity

Some advanced protections, including certain Safe Links, Safe Attachments, and impersonation-protection features, require Microsoft Defender for Office 365 or an eligible Microsoft 365 plan.

Technical controls should be supported by regular security awareness training. Employees need to know how to identify suspicious messages, unexpected login requests, fake invoices, unusual payment instructions, and attempts to impersonate company executives.

Employees should also have a simple way to report suspicious emails without worrying about being blamed. Reporting a questionable message early can help the business investigate and contain a potential threat before it spreads.

4. Protect Every Device That Accesses Microsoft 365

Microsoft 365 may operate in the cloud, but employees still access it through laptops, desktop computers, tablets, and mobile phones. An unprotected device can become an entry point to company data.

This risk increases when employees work remotely or use personal devices. For example, an employee may download a confidential document to an unsecured home computer or save company data in an unapproved application for convenience.

Every device that accesses company information should meet basic security requirements.

These requirements should include:

• Current operating system and application updates
• Endpoint security or antivirus protection
• Device encryption
• Automatic screen locking
• Strong sign-in credentials
• Secure Wi-Fi connections
• The ability to remotely remove business data from lost or stolen devices

Businesses should also maintain an accurate inventory of the devices that can access company resources. If the business does not know which devices are connected, it cannot confirm that those devices are properly protected.

Microsoft 365 Business Premium includes additional device management capabilities through Microsoft Intune and Microsoft Defender for Business. These tools can help organizations apply security policies, evaluate device compliance, and protect company information across supported devices.

5. Control File Sharing and Maintain Independent Backups

OneDrive and SharePoint make it easy for employees to collaborate and share files. That convenience can create risk when files are shared publicly, links remain active indefinitely, or users receive broader access than they need.

Small businesses should review their file-sharing settings and establish clear rules for sharing sensitive information.

Recommended practices include:

• Restrict anonymous or public sharing links.
• Use links that require the recipient to sign in.
• Set expiration dates for external sharing.
• Review access to sensitive folders regularly.
• Remove access when it is no longer required.
• Use sensitivity labels when available.
• Apply Data Loss Prevention policies where appropriate.

Businesses must also understand the difference between Microsoft’s retention capabilities and a complete backup strategy.

Microsoft provides several retention and recovery features, but businesses should not assume these features cover every situation. Accidental deletion, malicious employee activity, account compromise, and ransomware can create recovery needs beyond normal retention settings.

An independent cloud-to-cloud backup solution can provide additional protection for:

• Exchange Online email
• Calendars
• Contacts
• OneDrive files
• SharePoint data
• Microsoft Teams content, where supported

Backups should be automatic, monitored, and tested regularly. A backup is only useful if the business can restore the required information when an incident occurs.

Microsoft 365 Security Is a Shared Responsibility

Microsoft protects the infrastructure that supports Microsoft 365, including its cloud platform and data centers. Your business remains responsible for how users, accounts, permissions, devices, and company data are managed.

This shared responsibility means that using Microsoft 365 does not automatically eliminate security risks. Default settings may provide a useful starting point, but they may not fully address your organization’s operations, compliance obligations, insurance requirements, or exposure to cyber threats.

Microsoft 365 security should therefore be treated as an ongoing business process rather than a one-time technical setup.

Your business should regularly:

• Review user accounts and administrator privileges.
• Check that MFA remains enforced.
• Investigate unusual sign-in activity.
• Confirm that devices meet security requirements.
• Review external file-sharing permissions.
• Update phishing protections and employee training.
• Test backup and recovery procedures.

As your workforce, technology, and security risks change, your Microsoft 365 configuration should change with them.

Start With the Highest-Impact Protections

If your business has limited time or resources, begin with the controls that address the most common Microsoft 365 security gaps:

1. Require MFA for every user.
2. Reduce the number of administrator accounts.
3. Strengthen email and phishing protection.
4. Secure every device that accesses company data.
5. Control file sharing and maintain independent backups.

These actions create multiple layers of protection. If one security measure fails, another may still prevent an account compromise from becoming a serious business incident.

If you are unsure whether these protections are configured correctly, consider having your Microsoft 365 environment assessed by a qualified IT professional or managed IT service provider. A professional security review can identify weak settings, unnecessary permissions, unprotected devices, and gaps in backup coverage before they lead to data loss or business disruption.

Frequently Asked Questions About Microsoft 365 Security

Is Microsoft 365 secure enough for a small business?

Microsoft 365 includes built-in security capabilities such as anti-spam, anti-malware, anti-phishing protection, and security defaults. However, these features must be configured and managed correctly. Your business remains responsible for its user accounts, permissions, connected devices, file-sharing settings, and data protection practices.

Should every Microsoft 365 user have MFA?

Yes. MFA should be required for every user, including employees, executives, administrators, contractors, and temporary workers. Leaving even one account protected only by a password can create an avoidable entry point for attackers.

What is the biggest Microsoft 365 security risk?

Phishing and stolen user credentials are among the most serious risks. An attacker who gains access to a legitimate account may be able to read emails, impersonate the user, access stored files, and target the company’s customers or suppliers.

Does Microsoft 365 automatically back up all business data?

Microsoft offers retention and recovery capabilities, but these should not automatically be treated as a complete independent backup solution. Businesses should evaluate a separate cloud-to-cloud backup service based on their recovery needs, retention requirements, and risk profile.

How often should Microsoft 365 security settings be reviewed?

Security settings should be monitored continuously where possible and reviewed formally at regular intervals. A review should also be completed after staffing changes, a security incident, the introduction of new devices, or significant changes to the company’s Microsoft 365 environment.

Which Microsoft 365 plan offers the best security for small businesses?

Microsoft 365 Business Basic and Business Standard include important baseline protections. Microsoft 365 Business Premium includes additional capabilities for identity protection, device management, endpoint security, and advanced threat protection. The most appropriate plan depends on the business’s size, risks, regulatory requirements, and IT environment.