Microsoft 365 Security Features Every Business Should Enable

Microsoft 365 is the productivity backbone of hundreds of thousands of UK businesses. From email and calendar management in Outlook to file storage in OneDrive and SharePoint, team collaboration in Microsoft Teams, and document creation in Word, Excel, and PowerPoint, it is the single most important software platform for most SMEs. Yet despite this critical dependence, a staggering number of UK businesses are running Microsoft 365 with its default security settings — leaving significant vulnerabilities that could be closed with features they are already paying for.

This is not about purchasing additional security products. Microsoft 365 includes a remarkable array of security features within its standard business licences — features that many organisations simply never enable because they are not aware they exist, or because they assume Microsoft’s default configuration is sufficient. It is not. The default settings prioritise ease of use and compatibility, not security. Configuring Microsoft 365 for genuine security requires deliberate action.

This guide walks through the essential Microsoft 365 security features that every UK business should enable, explains what each feature does and why it matters, and provides practical guidance on implementation. Whether you are using Microsoft 365 Business Basic, Business Premium, or an Enterprise plan, there are security improvements you can make today that will significantly reduce your risk exposure.

1. Multi-Factor Authentication (MFA)

Multi-factor authentication is the single most impactful security measure you can implement in Microsoft 365. It requires users to verify their identity with a second factor — typically a code from an authenticator app on their phone — in addition to their password. If a password is compromised through phishing, a data breach, or brute-force attack, the attacker still cannot access the account without the second factor.

Microsoft’s own data shows that MFA prevents 99.9% of account compromise attacks. Despite this, surveys consistently show that around 40% of UK SMEs using Microsoft 365 have not enabled MFA for all users. This is the security equivalent of leaving the front door unlocked because it is easier than carrying a key.

Microsoft 365 includes MFA at no additional cost with every business licence. The recommended approach is to use Microsoft Entra ID (formerly Azure Active Directory) Security Defaults, which enforces MFA for all users. For businesses that need more granular control, Conditional Access policies (available in Business Premium and Enterprise plans) allow you to define specific conditions under which MFA is required.

2. Conditional Access Policies

Conditional Access is the next step beyond basic MFA. Available in Microsoft 365 Business Premium and Enterprise plans, Conditional Access policies allow you to define sophisticated rules that control who can access what, from where, on which devices, and under what conditions.

For example, you can create policies that require MFA for all access from outside the UK, block access from countries where your business does not operate, require compliant devices (devices that meet your security standards) for access to sensitive data, block legacy authentication protocols that do not support MFA, and require MFA for all administrative actions. These policies create a zero-trust security model where every access request is evaluated based on multiple signals — user identity, device health, location, and risk level — before being granted.

3. Email Security: Anti-Phishing and Safe Links

Email remains the primary attack vector for UK businesses. Phishing emails that impersonate trusted senders, contain malicious links, or carry infected attachments are the starting point for the majority of cyber attacks. Microsoft 365 includes several email security features that, when properly configured, provide robust protection.

Exchange Online Protection (EOP) is included in all Microsoft 365 plans and provides baseline anti-spam, anti-malware, and anti-phishing protection. However, EOP with its default settings is not sufficient for modern threats. Businesses should also configure anti-phishing policies to protect against impersonation attacks, Safe Links to scan URLs in emails and Office documents in real time, Safe Attachments to detonate suspicious attachments in a sandbox before delivery, and DMARC, DKIM, and SPF records to prevent domain spoofing.

4. Data Loss Prevention (DLP)

Data Loss Prevention policies help prevent sensitive information from being shared outside your organisation. DLP can detect and block emails, files, and chat messages that contain sensitive data types such as credit card numbers, National Insurance numbers, passport numbers, and other personal data covered by GDPR.

For UK businesses subject to GDPR, DLP is a valuable compliance tool. You can create policies that warn users when they are about to share sensitive information externally, require justification for the sharing, or block the action entirely. DLP policies can be applied across Exchange Online, SharePoint Online, OneDrive for Business, and Microsoft Teams, providing consistent protection regardless of how data is being shared.

5. Mobile Device Management with Intune

With hybrid and remote working now standard for UK businesses, company data inevitably ends up on mobile phones and personal devices. Microsoft Intune, included in Microsoft 365 Business Premium, allows you to manage and secure these devices without invading user privacy.

At a minimum, you should configure app protection policies that prevent corporate data from being copied to personal apps, require a PIN or biometric to access company data on mobile devices, and enable remote wipe of company data if a device is lost or an employee leaves. These policies can be applied to both company-owned and personal (BYOD) devices, protecting corporate data whilst respecting the user’s personal content.

6. SharePoint and OneDrive Sharing Controls

By default, Microsoft 365 allows users to share files and folders externally with almost no restrictions. This is convenient but creates significant data leakage risks. A single user sharing a folder with “anyone with the link” can inadvertently expose sensitive business data to the entire internet.

You should configure external sharing policies to restrict who can share externally, what can be shared, and with whom. At minimum, disable “Anyone” links (which require no authentication), require external recipients to verify their identity, set expiration dates on sharing links, and audit external sharing activity regularly. These controls balance the genuine business need for external collaboration with the security requirement to protect sensitive data.

7. Audit Logging and Alerting

Microsoft 365 generates a wealth of audit data that can help you detect suspicious activity, investigate incidents, and demonstrate compliance. Unified audit logging captures events across Exchange Online, SharePoint, OneDrive, Teams, Azure AD, and other Microsoft 365 services.

Beyond passive logging, you should configure alert policies for high-risk events. Microsoft 365 includes built-in alert policies for events such as unusual volume of file deletion, creation of forwarding rules (a common indicator of compromise), elevation of privileges, and sign-in from unusual locations. These alerts should be directed to your IT team or managed service provider for prompt investigation.

Getting Started: A Priority-Based Approach

Implementing all of these security features at once can be overwhelming, especially for businesses without dedicated IT staff. The good news is that you do not need to do everything on day one. A phased approach, starting with the highest-impact measures, is both practical and effective.

Week one should focus on MFA — enabling it for all users is the single most impactful action you can take. Week two should address email security — configuring anti-phishing policies, Safe Links, and Safe Attachments. Week three should tackle sharing controls and basic DLP. Weeks four and beyond can address Conditional Access, device management, and advanced monitoring.

Each of these measures reduces your risk exposure significantly. Combined, they transform Microsoft 365 from a potentially vulnerable platform into a genuinely secure one. And because all of these features are included in Microsoft 365 Business Premium (currently around £19.70 per user per month), there is no additional software cost — only the time and expertise required to configure them properly.

For businesses that lack the internal expertise to implement these security measures, a managed IT provider can configure everything on your behalf, typically within a few days. The investment is modest compared to the potential cost of a data breach, and it demonstrates the due diligence that GDPR and Cyber Essentials require.