Best Practices for SharePoint Online Security

SharePoint Online is a powerful cloud-based collaboration platform, but without proper security measures, it can be vulnerable to unauthorized access, data leaks, and cyber threats. Organizations must implement best practices to protect sensitive data, manage user access, and enforce compliance policies.

This guide provides step-by-step security best practices for SharePoint Online.

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1. Manage User Access and Permissions

Controlling who has access to SharePoint sites, libraries, and files is crucial for security.

✔ Use Groups Instead of Assigning Permissions to Individuals

• Assign users to SharePoint groups instead of granting permissions individually.
• Use default groups like Owners, Members, and Visitors for easy management.

✔ Apply the Principle of Least Privilege (PoLP)

• Grant the minimum permissions necessary.
• Regularly review user access levels.

✔ Restrict External Sharing

• Go to SharePoint Admin Center → Policies → Sharing.
• Limit sharing to specific external domains.
• Disable anonymous links where unnecessary.

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2. Secure External Sharing and Guest Access

External sharing allows collaboration with clients, vendors, and partners, but it should be controlled to prevent data leaks.

✔ Configure External Sharing Policies

• Set external sharing to “New and existing guests” instead of “Anyone”.
• Require guests to sign in using Microsoft or work accounts.

✔ Expire External Access Automatically

• Set expiration dates for guest access.
• In Microsoft 365 Admin Center → Security & Compliance, enforce expiration policies.

✔ Monitor External Sharing Activity

• Use Microsoft Purview Audit Logs to track external sharing events.

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3. Enable Multi-Factor Authentication (MFA)

MFA adds an extra layer of security by requiring users to verify their identity with a second factor (e.g., phone, authenticator app).

✔ How to Enable MFA for SharePoint Users

1. Go to Microsoft Entra Admin Center → Security.
2. Select Conditional Access → Create a policy.
3. Choose Users and Groups → All users.
4. Under Grant, select Require Multi-Factor Authentication.
5. Click Enable.

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4. Configure Conditional Access Policies

Conditional Access ensures that only trusted devices and locations can access SharePoint Online.

✔ Create Conditional Access Rules

• Block sign-ins from high-risk locations.
• Require device compliance for SharePoint access.
• Restrict access to managed devices only.

✔ Steps to Implement Conditional Access

1. Open Microsoft Entra Admin Center.
2. Navigate to Security → Conditional Access.
3. Create a new policy, select SharePoint Online as the target app.
4. Define conditions (e.g., block access from unknown locations).
5. Apply controls (e.g., require MFA or approved devices).

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5. Monitor and Audit User Activity

Tracking user activity helps identify suspicious behavior and security risks.

✔ Enable Unified Audit Logs

1. Go to Microsoft Purview Compliance Portal.
2. Click Audit → Turn on Audit Logging.
3. Review user activities (file downloads, permission changes, logins).

✔ Set Up Alerts for Suspicious Activity

• Use Microsoft Defender for Office 365 to create alerts for unusual access patterns.
• Set alerts for mass file deletions or sharing sensitive files externally.

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6. Protect Sensitive Data with Information Protection Policies

Data classification and labeling help secure sensitive documents.

✔ Enable Sensitivity Labels

1. Open Microsoft Purview Compliance Portal.
2. Navigate to Information Protection → Sensitivity Labels.
3. Create labels like Confidential, Internal, Public.
4. Apply policies to encrypt and restrict document access.

✔ Use Data Loss Prevention (DLP) Policies

1. Go to Microsoft Purview Compliance → Data Loss Prevention.
2. Create policies to prevent sharing credit card numbers, SSNs, or confidential data.
3. Block external sharing of sensitive documents automatically.

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7. Secure SharePoint Online with Advanced Threat Protection (ATP)

Microsoft Defender for Office 365 helps protect SharePoint Online from malware and phishing attacks.

✔ Enable Safe Attachments and Safe Links

1. Go to Microsoft Defender Admin Center.
2. Click Policies & Rules → Threat Policies.
3. Enable Safe Attachments to scan files for malware.
4. Enable Safe Links to block malicious URLs in SharePoint files.

✔ Block File Uploads Based on File Type

1. Open SharePoint Admin Center.
2. Go to Settings → Security & Compliance.
3. Create a rule to block uploads of executable files (e.g., .exe, .js).

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8. Regularly Review Security and Compliance Reports

Reviewing security reports ensures ongoing protection.

✔ Use SharePoint Security Reports

• Open Microsoft 365 Security & Compliance Center.
• Go to Reports > Security & Risk Dashboard.
• Monitor failed sign-ins, permission changes, and file access logs.

✔ Conduct Regular Security Audits

• Review guest access lists and external sharing links quarterly.
• Remove inactive users from SharePoint sites.