Phishing attacks are one of the most common cybersecurity threats, targeting users through deceptive emails to steal credentials, inject malware, or compromise sensitive data. Microsoft Defender for Office 365 offers robust security features to detect, prevent, and respond to phishing threats.
🔹 Key Strategies to Protect Email from Phishing with Microsoft Defender
1️⃣ Enable Anti-Phishing Policies in Microsoft Defender
Microsoft Defender automatically analyzes email behavior, impersonation patterns, and sender reputation to detect phishing attempts.
✔ Configure Anti-Phishing Protection
1️⃣ Go to Microsoft Defender Security Portal
2️⃣ Navigate to: Email & Collaboration > Policies & Rules > Threat Policies
3️⃣ Select Anti-Phishing
4️⃣ Set Up Protection Against:
- User & domain impersonation
- Spoof intelligence
- Mailbox intelligence for anomaly detection
- Authentication failures (SPF, DKIM, DMARC)
✅ PowerShell to Enable Anti-Phishing Policies
powershellCopyEditSet-AntiPhishPolicy -Identity "Default" -EnableMailboxIntelligenceProtection $true -EnableTargetedUserProtection $true -EnableOrganizationDomainsProtection $true
2️⃣ Implement Advanced Threat Protection (ATP) Safe Links & Safe Attachments
Microsoft Defender provides Safe Links and Safe Attachments to scan URLs and files in real-time before users open them.
✔ Enable Safe Links (Protects URLs in Emails & Office Documents)
1️⃣ Go to: Microsoft Defender Security Portal
2️⃣ Navigate to: Threat Policies > Safe Links
3️⃣ Create a Safe Links Policy:
- Enable URL scanning for emails and Office apps
- Prevent users from clicking malicious links
- Enable time-of-click protection
✅ PowerShell to Enable Safe Links for Email Protection
powershellCopyEditNew-SafeLinksPolicy -Name "SafeLinksPolicy" -EnableForEmail $true -EnableForOffice $true
✔ Enable Safe Attachments (Protects Against Malicious Files)
1️⃣ Go to: Microsoft Defender Security Portal
2️⃣ Navigate to: Safe Attachments
3️⃣ Turn On:
- Dynamic Analysis to scan file behavior
- Zero-hour Auto Purge (ZAP) to remove malicious emails post-delivery
✅ PowerShell to Enable Safe Attachments
powershellCopyEditSet-SafeAttachmentsPolicy -Identity "SafeAttachmentsPolicy" -Enable $true -Action Block
3️⃣ Strengthen Email Authentication with SPF, DKIM & DMARC
Email authentication ensures only legitimate senders can send emails on behalf of your domain.
✔ Implement SPF (Sender Policy Framework)
SPF prevents spoofing by verifying if an email originated from an authorized server.
✅ PowerShell to Configure SPF
powershellCopyEditSet-DkimSigningConfig -Identity contoso.com -Enabled $true
👉 Add this TXT record to DNS:
txtCopyEditv=spf1 include:spf.protection.outlook.com -all
✔ Enable DKIM (DomainKeys Identified Mail)
DKIM ensures email integrity by adding an encrypted signature to each email.
✅ PowerShell to Enable DKIM
powershellCopyEditSet-DkimSigningConfig -Identity contoso.com -Enabled $true
✔ Enforce DMARC (Domain-based Message Authentication, Reporting, & Conformance)
DMARC prevents domain spoofing and reports unauthorized email activity.
✅ DMARC DNS TXT Record:
txtCopyEditv=DMARC1; p=quarantine; rua=mailto:[email protected]
4️⃣ Block High-Risk Attachments & Executable Files
Attackers use malicious attachments to deploy ransomware and trojans.
✔ Block Suspicious File Types in Defender
1️⃣ Go to: Security Portal > Threat Policies > Anti-Malware
2️⃣ Enable Real-Time Protection & Block Attachments:
- .exe, .js, .vbs, .bat, .cmd, .scr
- Compressed file types (.zip, .rar)
✅ PowerShell to Block High-Risk Attachments
powershellCopyEditSet-MalwareFilterPolicy -Identity "Default" -EnableFileFilter $true -FileTypes exe,js,vbs,bat,cmd,scr,zip,rar
5️⃣ Configure Microsoft Defender Attack Simulation Training
Users are the weakest security link—90% of successful attacks result from human error.
Microsoft Defender offers simulated phishing attacks to train employees.
✔ Create a Phishing Attack Simulation in Defender
1️⃣ Go to: Microsoft Defender Portal > Attack Simulation Training
2️⃣ Launch a Simulation
3️⃣ Target Specific Users & Departments
4️⃣ Analyze Who Clicked the Phishing Link & Failed
✅ PowerShell to Get Users Who Clicked on Phishing Emails
powershellCopyEditGet-MailDetailATPReport -StartDate "03/01/2024" -EndDate "03/10/2024" -EventType Click
6️⃣ Block International & High-Risk IPs Using Conditional Access
Many phishing attacks originate from foreign IPs or anonymous proxies.
✔ Restrict Login Attempts from High-Risk Countries
✅ PowerShell to Block All Non-US Logins
powershellCopyEditNew-AzureADConditionalAccessPolicy -DisplayName "Block Non-US Access" -State Enabled -Conditions @{
UserRiskLevels = @("high")
Locations = @("All Except US")
Applications = @("Exchange Online")
} -GrantControls @("BlockAccess")
✔ Enable Risk-Based MFA
Force Multi-Factor Authentication (MFA) on risky sign-ins.
✅ PowerShell to Require MFA for High-Risk Users
powershellCopyEditSet-AuthenticationPolicy -Identity Default -AllowBasicAuthIMAP $false -AllowBasicAuthPOP $false
🔹 Final Best Practices to Secure Email from Phishing
✔ Enable Microsoft Defender XDR to correlate phishing threats across email, identity, and devices.
✔ Use Power Automate to quarantine suspicious emails automatically.
✔ Monitor Suspicious Email Forwarding Rules—attackers create auto-forwarding rules to exfiltrate emails.
✔ Review Email Logs in Defender Portal to detect suspicious login activity.
✔ Automate Incident Response using Microsoft Sentinel for real-time detection and alerting.
✅ Conclusion
Microsoft Defender for Office 365 provides AI-driven, multi-layered protection against phishing. By leveraging anti-phishing policies, Safe Links, Safe Attachments, SPF/DKIM/DMARC, and PowerShell automation, organizations can significantly reduce phishing risks and improve email security.
🚀 Next Steps:
🔹 Enable Anti-Phishing Policies in Microsoft Defender
🔹 Set Up Safe Links & Safe Attachments to block malicious content
🔹 Implement SPF, DKIM, and DMARC for sender authentication
🔹 Simulate phishing attacks using Microsoft Attack Simulation Training
🔹 Automate security incident response with PowerShell
💬 Have you encountered phishing attempts in your organization? How do you mitigate them? Share your experience! 🚀