Continuous Monitoring of M365 Security in an SME in 2026

Microsoft 365 is at the heart of the business for many SMEs: emails, documents, Teams conversations and user account management all go through the same platform. This concentration makes the M365 environment an attractive target for attackers. One-off security configuration checks are not enough, as threats evolve and your environment changes daily.

In this article, we'll walk you through how to build an M365 security monitoring model that works for your SMB. You'll learn how to identify key risks, automate alerts and create clear remediation paths for your rapidly growing teams. Vahti provides Finnish SMEs with the tools to monitor their M365 environment without deep technical expertise.

Key findings: Monitoring M365 security in an SME in 2026

• Monitoring the M365 environment requires continuity, as settings become outdated and risks change daily.
• Identity attacks are the most common threat: more than 97% of account breaches are based on weak or reused passwords.
• Automated monitoring and alerts significantly reduce response time compared to manual monitoring.
• Vahti helps SMEs see the true state of security in their M365 environment and prioritises risks into a clear remediation list.
• Clear remediation paths and responsible parties ensure that identified risks are remediated in a timely manner.

Why is M365 security monitoring essential for SMEs?

Microsoft 365 environments are under constant attack. According to the Centre for Cyber Security, more than 330 M365 account intrusion incidents were reported in Finland in 2025. The situation has accelerated, with 121 incidents reported in a single month in October 2025.

Attackers are not only targeting large enterprises. SMEs are an attractive target because they often have limited resources for monitoring. An attack can start with a single hijacked account and quickly spread throughout an organisation.

What happens when an M365 account is hijacked?

A hijacked account gives an attacker access to emails, files and Teams conversations. The attacker can send credible phishing messages to colleagues and customers using the correct email address. This makes the scams difficult to identify.

Billing scams are common: the attacker monitors email traffic, identifies payment-related conversations and sends a fake invoice from an address that looks real. The damage can be significant before the breach is even detected.

Why are one-off settings not enough?

The M365 environment changes, even if you do nothing. Microsoft regularly releases new features and security settings. Users add applications, share files and change settings. Each change can open a new risk path.

Unchecked, these changes will go unnoticed. Monitoring reveals anomalies and allows you to react before the risk becomes a liability.

What are the most common M365 security risks for SMEs?

The risks in an M365 environment are similar across organisations of all sizes. By prioritising correctly, you can significantly reduce risk without heavy projects.

Identity attacks

Username is the most common route into the M365 environment. According to Microsoft's Digital Defense Report 2025, more than 97% of identity attacks are based on password attacks, which attempt weak or reused passwords. Multi-factor authentication (MFA) prevents more than 99 percent of unauthorized login attempts.

The risk increases if MFA is not comprehensively implemented or is implemented too loosely. Maintenance domains in particular require stronger protection, as they give an attacker broad access rights.

Phishing and email spoofing

Phishing is still the most common form of attack. By 2024, as many as 74% of organisations will report being the target of a phishing attack. AI-generated phishing messages are becoming more credible and harder to identify.

Business Email Compromise (BEC) scams exploit hijacked accounts. The attacker poses as a trusted individual and requests urgent payment or release of information. Without clear policies and verification procedures, these scams are all too often successful.

File sharing and excessive permissions

SharePoint and OneDrive make sharing easy. The risk arises when sharing is not controlled and monitored. Typical problems include:

• External sharing is allowed without clear limits
• Link sharing allows access to a wider area than intended
• Existing sharing rights remain in force when projects end
• Sensitive information is stored in public libraries without classification

These problems will not be solved by kiosks. You need a model where you define the limits of permissible sharing and monitor compliance.

Third party applications

Users can connect third-party applications to their M365 environment that are granted extensive rights to data. Without control, you don't know which applications are in use and what rights they have. Vahti shows you all the applications that are connected and reveals the risks associated with them.

How do you build a working M365 security monitoring model?

A working control model combines technical controls, automated alerts and clear policies. Start with the basics and expand step-by-step.

Step 1: Establish identity protection

Identity is the foundation of M365 security. Start with these steps:

1. Enable MFA for all users. Start with administrative domains and expand to the entire organization. Use phishing-resistant methods wherever possible.
2. Use as many methods as possible to secure access. Restrict logins based on risk: block logins from unknown countries, require stronger authentication for maintenance operations.
3. Restrict administrator rights. Grant administrative rights only when necessary and preferably for a limited period of time. Avoid permanent administrator roles.
4. Enable login logging. Monitor logins and set alerts for suspicious events.

Step 2: Improve email security

Email is the most common avenue of attack. Strengthen your protection with these steps:

1. Configure email authentication. SPF, DKIM and DMARC block fake emails that appear to come from your organization.
2. Enable anti-malware and anti-fishing. Microsoft Defender for Office 365 provides Safe Links and Safe Attachments protection.
3. Create a clear reporting process. Determine how to report a suspicious message and how IT will respond. Test the process regularly.

Step 3: Information management policies

Manage information sharing and storage with clear policies:

1. Define the boundaries of external sharing. Decide what information can be shared externally and under what conditions.
2. What information is shared and how it is shared. Remove outdated sharing links and guest user permissions.
3. Classify sensitive data. Use identification labels to mark data that require special protection.

How do you automate control of your M365 environment?

Manual monitoring does not scale to the needs of a growing organization. Automation ensures that critical events are detected in a timely manner.

Configuring alerts in Microsoft 365

Microsoft 365 provides built-in alerts that you can enable in the Defender portal. Configure alerts for these events:

• Suspicious logins from unknown locations
• Multiple unsuccessful logon attempts
• Creation of mailbox forwarding
• Bulk downloads from OneDrive or SharePoint
• Setting up a new administrator role

Alerts are only useful if they are acted upon. Assign a responsible person and a policy for each alert.

Simplify monitoring with Vahti

Vahti provides an easy way for SMEs to monitor their M365 environment. Vahti analyses the security settings and risk signals in your environment, prioritises findings in order of criticality and provides clear remediation instructions. You don't need to be an IT expert to understand what to do.

Guard monitors logins, permissions, applications and settings around the clock. Anomalies are detected before they become problems. This frees up your time to focus on business instead of security concerns.

How do you define clear remediation paths for identified risks?

Risk detection is just the beginning. Real value is created when risks are also remediated. Clear remediation paths ensure that action follows from the findings.

Building the remediation process

An effective remediation process includes these steps:

1. Prioritization: rank risks by severity and likelihood. Fix the most critical ones first.
2. Assignresponsibility: for each risk, assign a person responsible for remediation.
3. Guidance: provide clear step-by-step instructions for corrective action.
4. Follow-up: Ensure that the repair has been carried out and document the outcome.

Practical steps to repair a Vahti

For each risk, Vahti shows what needs to be done and how. The repair instructions are written in plain language, so you don't need deep technical knowledge. You can carry out the repairs yourself or pass the repair request on to an expert.

This model ensures that risks are not left hanging. Every observation leads to a concrete action and a documented outcome.

How do you respond quickly to an M365 security incident?

When an anomaly is detected, responding quickly limits damage. Have a plan of action in place so that in the event of a crisis, you don't have to think about the next step.

The first 30 minutes of response

Critical first steps in the event of a break-in:

1. Prevent access. Change user password and cancel active sessions immediately.
2. Check for damage. Find out what data may have been seen or downloaded by the attacker.
3. If the user has accessed or accessed a file, see if he/she has accessed or accessed the data. Check mailbox forwards, delegations and OAuth applications.
4. Document. Record timeline and actions for later analysis.

Testing the business model

Practice outliers before they happen. Short tabletop exercises running through a realistic account breach scenario will expose weaknesses in the process. Correct shortcomings before a real crisis occurs.

How do staff competencies support M365 security?

Technical controls are essential, but they alone are not enough. Staff performance is often the deciding factor in whether or not an attack succeeds.

Training priorities

Focus on the practical situations that staff face in their day-to-day work:

• Identifying and reporting fishing messages
• Handling suspicious MFA requests
• Secure file sharing
• Verification procedures for payment requests

Role-specific training to increase effectiveness. Finance staff face different scams than the sales team. Tailor examples to the target audience.

Repetition and training

One-off training does not change behaviour permanently. Short, regular reminders and simulated fishing tests build lasting vigilance. See how the organisation evolves over time.

What does it take for an SME to implement M365 monitoring?

Launching monitoring does not require a large investment or IT department. Start with the basics and expand as needed.

Minimum start-up requirements

These steps will get you started:

1. MFA for all users. This single measure will prevent the vast majority of account breaches.
2. Basic alerts are enabled. Enable M365's built-in alerts for the most critical events.
3. Regular checks. Set aside time each month to review your settings and permissions.

Vahti deployment

Connect Vahti to your M365 environment in minutes. Simply give Vahti read-only access through the official Microsoft interfaces. Vahti does not make any changes to your environment, but provides a view of the actual state of your security and guides you through the remediation process.

You'll immediately get a clear picture of your risks and concrete steps to fix them. This is an efficient way to start monitoring M365 security without heavy projects.

How do you measure the progress of your M365 security?

Measurement makes progress visible and helps justify investments.

Key metrics

Track these metrics on a monthly basis:

• Number of open risks: How many identified risks are waiting to be remediated?
• Time to remediation: How quickly are risks remediated after detection?
• Number and quality of alerts: are the alerts relevant or are unnecessary alerts being generated?
• Results of fishing simulations: How do staff react to simulated attacks?

These metrics will tell you if your monitoring model is working and where there is room for improvement.

Summary: M365 security controls for SMEs 2026

Monitoring your M365 environment is not a one-off project, but a permanent approach. Threats are evolving and your environment is changing daily. An effective monitoring model combines identity protection, automated alerts, clear remediation paths and staff skills.

Start with the basics: MFA for all, basic alarms in place and regular checks. Expand in stages as needed. Vahti provides SMEs with an easy way to see the true state of security in their M365 environment and remediate risks in a timely manner.

Security is not a barrier to business. It is a prerequisite for trust and growth.

Frequently asked questions about M365 security controls

Why does the M365 environment require separate controls?

Microsoft is responsible for the infrastructure and availability of the platform, but the customer is responsible for their own data, usernames and settings. Monitoring exposes risks and changes that Microsoft does not automatically respond to.

Guard helps you see the true state of security in your M365 environment at a glance and prioritizes risks for remediation.

How quickly can M365 monitoring be deployed?

You can deploy basic monitoring in a matter of hours. Activating the MFA, configuring basic alerts and connecting Vahti to the environment are quick steps.

Connecting the Vahti to your M365 environment takes just a few minutes, and you'll get an instant view of your security posture.

What does it cost to monitor M365 security for an SME?

The cost depends on the implementation chosen. M365's built-in alerts are included in the basic licenses. Vahti offers SMBs user-based pricing that scales with the size of the organization.

Vahti charges based on active M365 users, and does not include guests or shared mailboxes.

How does monitoring differ from a one-off security audit?

An audit provides a snapshot of the situation at a single point in time. Monitoring monitors the environment around the clock and detects changes and anomalies in real time.

Guard monitors your M365 environment 24/7 and identifies risks before they become problems.

Do you need an IT expert for M365 monitoring?

Not necessarily. Vahti is designed so that even without deep technical knowledge, you understand the risks and can take action to address them. The remediation instructions are written in plain language, and you can forward a remediation request to an expert if necessary.