Microsoft 365 is the backbone of modern business collaboration, but its popularity makes it a prime target for cybercriminals. Recently, we’ve seen a surge in sophisticated attacks aimed at exploiting misconfigurations, user behaviour, and emerging vulnerabilities.
In this post, we’ll explore the top 10 security threats currently impacting Microsoft 365 environments and explain how our M365 Align service, powered by CIS tenant hardening, helps you stay secure.
The Top 10 Microsoft 365 Security Threats
1. Consent Phishing via OAuth Apps
Attackers trick users into granting permissions to malicious apps, enabling persistent access to data.
2. Business Email Compromise (BEC)
Fraudulent emails impersonate executives or vendors to request payments or sensitive information.
3. Token Theft in Microsoft Teams
Authentication tokens stolen from Teams desktop apps allow attackers to bypass MFA.
4. Ransomware Delivery via SharePoint and OneDrive
Malicious files uploaded internally spread ransomware across the organisation.
5. MFA Fatigue Attacks
Repeated MFA prompts wear down users until they approve one, leading to account compromise.
6. Exploitation of Conditional Access Misconfigurations
Weak or overly permissive policies allow attackers to bypass security controls.
7. Malicious Outlook Add-ins
Threat actors distribute harmful add-ins to steal credentials and maintain persistence.
8. Zero-Day Vulnerability in Exchange Online
Recently patched zero-day exploited for mailbox compromise and remote code execution.
9. AI-Powered Phishing Campaigns
Attackers use AI to craft highly convincing phishing emails targeting Microsoft 365 users.
10. Data Exfiltration via Power Automate Flows
Malicious flows move sensitive data outside the organisation without detection.
How M365 Align Can Assist in Mitigating Threats
M365 Align provides comprehensive protection against the most critical Microsoft 365 threats by applying CIS tenant hardening best practices. Our service enforces strict app consent controls and admin approval workflows to prevent OAuth abuse, while advanced anti-phishing policies, Safe Links, Safe Attachments, and email authentication standards (DMARC, DKIM, SPF) safeguard against BEC and AI-driven phishing attacks. Conditional Access policies with device compliance checks, MFA number matching, and risk-based sign-in protections defend against token theft and MFA fatigue. We also deploy Safe Attachments scanning for SharePoint and OneDrive, apply file type restrictions, and implement DLP policies to stop data exfiltration.
Why CIS Tenant Hardening Matters
The CIS benchmarks provide a globally recognised framework for securing Microsoft 365. By aligning your tenant with these standards, we:
- Reduce attack surface.
- Enforce consistent security controls.
- Improve compliance posture.
Ready to Secure Your Microsoft 365 Environment?
Cyber threats are evolving daily, but with M365 Align, your organisation stays ahead. Contact us today to learn how we can harden your Microsoft 365 tenant and protect your business from the latest attacks.
Book a call – Frontline Consultancy and Business Services Ltd
Article Written by Anthony Roberts – Head of Cloud Services
