Microsoft 365 Security Assessment: Is Your Business Fully Protected?

Objective

This guide explains what Microsoft 365 security assessments, its importance, and how to examine several critical Microsoft 365 security settings.

This guide will also describe how to begin evaluating security for identity and email, which are two attack vectors that are often overlooked.

Key Takeaways

• Microsoft 365 security requires ongoing review, not a one-time setup.
• A security assessment helps identify configuration weaknesses before they are exploited.
• The assessment should begin with the security of identity and email.
• The risk of business loss can multiply with small configuration errors.
• Ongoing assessments improve cyber resilience and compliance.

Introduction

Your staff logs into Microsoft 365 to send email, store files in OneDrive, communicate through Microsoft Teams, and manage documents in SharePoint. It is a trusted Microsoft platform, so it must be secure.

But here’s the thing: using Microsoft 365 does not automatically mean your environment is fully protected.

Microsoft secures the cloud platform. Organisations must secure the proper configuration of user access, permissions, sharing, security policies, and monitoring. There is a risk of exposure with each unconfigured security control. Microsoft states that Microsoft 365 is built with security in mind, but no platform is fully secure. The configuration will always need to be evaluated.

That is why a Microsoft 365 security assessment has become an important part of modern cybersecurity. Whether you run a growing business, manage a corporate IT environment, or prepare for ISO 27001 certification, reviewing your Microsoft 365 environment helps you identify security gaps before they become costly problems.

Table of Contents

• Why Microsoft 365 Security Matters More Than Ever
• What Is a Microsoft 365 Security Assessment?
• Signs Your Business Needs a Microsoft 365 Security Assessment
• Step 1: Review Identity and Access Security
• Step 2: Review Email Security
• Step 3: Review SharePoint and OneDrive Security
• Step 4: Review Microsoft Teams Security
• Step 5: Review Microsoft Defender Security
• Step 6: Review Microsoft Purview
• Professional Assessment vs Internal Review
• Microsoft 365 Security Is One Part of a Strong Cybersecurity Strategy
• Small Configuration Issues Can Create Larger Security Risks
• Protect Your Microsoft 365 Environment Before Problems Appear
• Frequently Asked Questions

Why Microsoft 365 Security Matters More Than Ever

Microsoft 365 has become the workplace for many Australian organisations.

Employees communicate through Microsoft Teams, exchange emails in Outlook, store documents in SharePoint Online, collaborate through OneDrive, and access business applications from almost anywhere.

While this flexibility improves productivity, it also increases the number of security settings that need careful management.

For example:

• New employees join every month.
• Contractors receive temporary access.
• Teams are created for new projects.
• Files are shared internally and externally.
• Users install third-party applications.

Without regular reviews, these changes can slowly create security gaps that nobody notices.

A business that looked secure two years ago may have dozens of inactive accounts, excessive permissions, or outdated security settings today.

Microsoft Secures the Platform. You Secure Your Environment.

One of the biggest misunderstandings about cloud services is assuming security is entirely Microsoft’s responsibility.

In reality, Microsoft protects the infrastructure, while customers are responsible for securing their users, their identities, their rights (permissions), their devices, and their business data. With respect to a Microsoft 365 security strategy, Microsoft calls for the adoption of the principles of Zero Trust, the least-privilege approach, and stronger identity security.

Consider the analogy of renting.

The landlord provides secure (protected) walls and locks along with maintenance.

Your business determines who gets keys, who can enter restricted areas, and where secure documents are stored.

What Is a Microsoft 365 Security Assessment?

A Microsoft 365 security assessment is a methodical examination of a Microsoft 365 environment to pinpoint security vulnerabilities and configuration, identity, and security posture-related concerns.

Rather than checking only one setting, the assessment reviews how different Microsoft 365 services work together.

A professional assessment commonly includes:

• Microsoft Entra ID
• Exchange Online
• Microsoft Teams
• SharePoint Online
• OneDrive
• Microsoft Defender
• Microsoft Purview

Borderless CS follows this approach by assessing these core Microsoft 365 components to identify security gaps and recommend improvements based on business risk.

Security Assessment vs Security Monitoring

Many organisations confuse these two services.

Both services are valuable, but they solve different problems.

An assessment tells you where weaknesses exist today, while monitoring helps identify suspicious behaviour after your environment is operational.

Signs Your Business Needs a Microsoft 365 Security Assessment

Not every security issue creates an immediate incident.

In many cases, businesses continue operating normally while hidden risks quietly build over time.

Here are some common signs that your Microsoft 365 environment should be reviewed.

Your Security Settings Haven’t Been Reviewed for Years

Many organisations configure Microsoft 365 during migration and rarely revisit those settings.

Since then:

• New Microsoft features have been released.
• Staff have changed roles.
• New applications have been connected.
• Business requirements have grown.

If no structured review has been completed recently, your current security settings may no longer reflect today’s risks.

Former Employees Still Have Active Accounts

Imagine an employee leaves the business.

Their mailbox is disabled, but administrator permissions remain active.

Months later, that account still appears in privileged access reports.

Situations like this happen more often than many organisations realise.

Regular identity reviews help identify unnecessary accounts and excessive permissions before they become a problem.

Multi-Factor Authentication Is Not Fully Enforced

Microsoft recommends protecting privileged accounts with multi-factor authentication and strengthening identity security through Conditional Access and secure authentication methods.

If some users still rely only on passwords, your organisation may face greater identity risk.

External Sharing Has Never Been Reviewed

Your business may share files with customers, suppliers, consultants, or contractors.

Over time, these permissions often accumulate.

Questions worth asking include:

• Who can access confidential files?
• Are guest users still required?
• Are sharing links set to expire?
• Can “Anyone with the link” still access sensitive documents?

Borderless CS recommends limiting external sharing, managing guest access, and applying controlled sharing settings across SharePoint Online and OneDrive environments.

Nobody Reviews Security Alerts

Microsoft Defender, Exchange Online, and Microsoft Entra generate valuable security information.

However, alerts only become useful when someone investigates them.

If alerts are ignored or reviewed only occasionally, important warning signs may be missed.

By recognising these warning signs early, organisations can improve Microsoft 365 security before small configuration issues develop into larger business risks.

Below is a more concise, AI SEO-friendly version of these sections. Each step is around 120–170 words, uses bullet points, answers the user’s question directly, and is easier for both readers and AI search engines to extract.

Step 1: Review Identity and Access Security

Microsoft 365 depends heavily on identity and access configurations. If an attacker subverts an account, then they will have access to email, files, Teams, and SharePoint without having to compromise your networks.

As a best practice, a Microsoft 365 security assessment should review your identity configurations to attest that only the right users have the appropriate access.

Evaluate the following:

• Microsoft Entra ID configuration
• User and admin accounts
• Multi-Factor Authentication (MFA)
• Conditional Access
• Guest and Inactive accounts
• Password Policies
• Legacy Authentication
• Privileged Role Assignments

For example, if an ex-contractor retains admin rights after leaving the firm, your system faces an avoidable threat. The purpose of frequent identity reviews is to eliminate stale accounts, reduce privileged access, and improve your security posture proactively to prevent an account security threat by an attacker.

Step 2: Review Email Security

As email is still the most prevalent attack vector, securing Office 365 is intrinsic to every Microsoft 365 security assessment and architecture. Compromise can originate from a single phishing email.

As part of your Microsoft 365 security assessment, verify the security of your configured email protection.

Check these security controls:

• Anti-phishing policies
• Anti-malware protection
• Safe Links and Safe Attachments
• Email authentication
• Mailbox auditing
• External forwarding rules
• Exchange Online security settings

For example, if mailbox auditing is disabled, investigating suspicious activity becomes much more difficult. Likewise, unrestricted email forwarding can allow sensitive business information to leave your organisation without anyone noticing. Regular reviews help ensure your email security settings continue to protect against modern threats.

Good Practice vs Common Security Risks

Step 3: Review SharePoint and OneDrive Security

SharePoint Online and OneDrive simplify file sharing, but leave confidential business data open to exposure with improper permissions.

A Microsoft 365 security assessment should examine file sharing practices, access permissions, and safeguarding of sensitive data.

Look into:

• External sharing settings
• Guest user access
• File and folder permissions
• Sharing link controls
• Link expiration policies
• Sensitive document libraries

Consider, for example, a project folder that is accessible to an external consultant and is continuously accessible to that consultant even after the conclusion of the project. Regularly reviewing permissions helps reduce access.

Step 4: Review Microsoft Teams Security

Microsoft Teams has become a central collaboration platform for many organisations. As more employees and external users work together through Teams, security settings should be reviewed regularly.

Assess the following:

• Guest access
• Team ownership
• External collaboration
• Third-party applications
• Meeting policies
• User permissions

Also check whether inactive Teams, unused guest accounts, and unnecessary permissions have been removed. Keeping Teams organised reduces security risks and makes administration easier. A regular review ensures collaboration remains secure without affecting employee productivity.

Step 5: Review Microsoft Defender Security

Microsoft Defender helps identify suspicious activity, malware, and other security threats across your Microsoft 365 environment. However, its value depends on correct configuration and ongoing monitoring.

During your assessment, review:

• Endpoint protection
• Malware detection
• Threat intelligence
• Security alerts
• Attack Surface Reduction rules
• Device visibility
• Microsoft Secure Score recommendations

For example, repeated failed sign-in attempts from unfamiliar locations may indicate suspicious activity. If security alerts are ignored, valuable warning signs can be missed. Regular reviews help ensure Defender provides meaningful protection instead of simply generating alerts that nobody investigates.

Step 6: Review Microsoft Purview

Microsoft Purview helps organisations protect sensitive business information by managing how data is classified, shared, and retained.

A Microsoft 365 security assessment should review whether your data protection policies match your business requirements.

Review these features:

• Data Loss Prevention (DLP)
• Sensitivity labels
• Retention policies
• Information classification
• Compliance Manager

For example, employee records, financial reports, customer information, and legal documents should not all have the same level of access. Applying the right protection controls reduces the risk of accidental or unauthorised data exposure while supporting compliance requirements.

Professional Assessment vs Internal Review

Many organisations perform basic Microsoft 365 checks internally, but an independent assessment often provides a broader view of security risks.

An internal review is useful for routine maintenance, while a professional Microsoft 365 security assessment offers a deeper analysis of your environment, helping identify configuration issues, strengthen security controls, and provide a practical roadmap for improvement.

Microsoft 365 Security Is One Part of a Strong Cybersecurity Strategy

A secure Microsoft 365 environment is important, but it should not operate in isolation.

Business security works best when different security services support one another.

For example:

Each service addresses a different part of your organisation’s security.

Together, they help reduce risk and improve cyber resilience.

If you are comparing providers that offer these services, our pillar guide, Top Cybersecurity Companies in Australia: How to Choose the Right Partner, explains what to evaluate before making a decision.

Small Configuration Issues Can Create Larger Security Risks

Many cyber incidents are not caused by one major mistake.

Instead, several small issues combine over time.

Imagine this scenario.

A former contractor still has an active account.

Multi-Factor Authentication is not enabled.

A SharePoint folder allows unrestricted sharing.

Mailbox auditing has never been enabled.

Individually, these issues may not seem urgent.

Together, they create unnecessary exposure.

A Microsoft 365 security assessment helps identify these small weaknesses before they become larger business problems.

Protect Your Microsoft 365 Environment Before Problems Appear

Borderless CS provides powerful collaboration and security features, but every organisation remains responsible for configuring and maintaining its own environment.

Regular assessments help answer important questions.

Who has access to sensitive information?

Are administrator accounts properly managed?

Can guest users still access confidential files?

Are email protections configured correctly?

Is sensitive business information adequately protected?

By reviewing identity, email, SharePoint, Teams, Defender, and Purview together, organisations gain a clearer understanding of their current security posture and the improvements that matter most.

The goal is not simply to pass a compliance review. It is to reduce business risk and build a stronger security foundation for the future.

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