Microsoft 365 is often the first and sometimes the only security control many SMBs rely on.
Email filtering is enabled. MFA is turned on. Microsoft Defender is active.
On paper, this feels secure.
In reality, Microsoft 365 was built to enable productivity, not to act as a complete security platform. Attackers know this, and they actively design their campaigns around its blind spots.
The Misconception Around Microsoft 365 Security
Microsoft provides a shared responsibility model. They secure the infrastructure, availability, and core services.
Security inside your tenant is your responsibility.
This distinction is often misunderstood by SMBs. Many assume that paying for Microsoft 365 automatically means threats are handled.
It does not.
Microsoft 365 security features are:
- Baseline protections
- Largely reactive
- Heavily dependent on correct configuration
Without continuous monitoring and correlation, serious threats go unnoticed.
Email Security Is Only the First Layer
Most SMBs focus on email filtering, and for good reason.
Phishing remains the top attack vector.
However, modern attacks often bypass email entirely:
- Credential reuse from breached services
- OAuth abuse
- Token theft
- Browser-based malware
- MFA fatigue attacks
Microsoft 365 does not provide full visibility into endpoint behaviour or post-compromise activity by default.
Once credentials are abused, attackers often operate quietly inside the tenant.
Identity Is the New Perimeter
Microsoft itself has acknowledged that identity is now the primary attack surface.
https://www.microsoft.com/security/blog/identity-is-the-new-perimeter/
Yet many SMBs still rely on:
- Single-factor authentication for legacy apps
- Excessive user permissions
- Long-lived sessions and tokens
- Limited audit log retention
These gaps allow attackers to move laterally without triggering obvious alerts.
Limited Visibility After Compromise
Even with Defender enabled, many SMBs lack answers to basic questions:
- Which device initiated this login?
- Was the browser compromised?
- Is this behaviour normal for this user?
- Has this access pattern changed recently?
Microsoft 365 focuses on alerts, not context.
Alerts without context are often ignored, misunderstood, or actioned too late.
Real-World Impact on SMBs
Industry research shows that a large percentage of breaches involving cloud platforms start with stolen credentials rather than malware.
https://www.verizon.com/business/resources/reports/dbir/
Once inside, attackers:
- Create inbox rules to hide activity
- Register new MFA methods
- Access SharePoint and OneDrive data
- Use trusted cloud infrastructure to persist
These actions often blend in with legitimate user behaviour.
Why Configuration Alone Is Not Enough
Many SMBs attempt to solve the problem by tightening policies.
Conditional access rules are added. Password policies are strengthened. Alerts are enabled.
This helps, but it does not address the root issue.
Security is not a checklist. It is an ongoing process of visibility, detection, and response.
Without monitoring endpoints, correlating identity events, and understanding behaviour, configuration only delays compromise.
What a Practical Security Layer Looks Like
Effective security for Microsoft 365 environments requires additional layers:
Endpoint Visibility
Knowing what is happening on the device is just as important as what happens in the cloud.
Behavioural Monitoring
Detecting anomalies in login patterns, access locations, and usage behaviour.
External Exposure Awareness
Understanding whether credentials, domains, or assets are already exposed externally.
Automated Remediation
Reducing manual response time when suspicious activity is detected.
How AIOpenSec Complements Microsoft 365
AIOpenSec does not replace Microsoft 365. It strengthens it.
- Endpoint monitoring provides device-level context
- External exposure assessments identify identity risk early
- Automated patching reduces attack surface
- A-Monk explains risks and actions in plain language
This gives SMBs the missing layer between cloud productivity and real security operations.
Final Thoughts
Microsoft 365 is a powerful platform, but it was never meant to operate alone as a security strategy.
Attackers understand its limits and exploit them daily.
For SMBs, the goal is not to abandon Microsoft 365, but to recognise its boundaries and build visibility around it.
Security starts where assumptions end.
And assumptions are exactly what attackers rely on.