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In this blog post, we’ll walk through practical strategies to reduce the likelihood and impact of successful AiTM (Adversary-in-The-Middle) phishing attacks in Microsoft 365.
🔗 Reference: Microsoft 365: Protect your environment against AiTM phishing attacks
You Should Know:
1. Enable Multi-Factor Authentication (MFA)
MFA is critical in preventing unauthorized access. Use Conditional Access Policies to enforce MFA for all users.
PowerShell Command:
Set-MsolUser -UserPrincipalName [email protected] -StrongAuthenticationRequirements @{State="Enabled"}
2. Implement Conditional Access Policies
Restrict access based on location, device compliance, and risk levels.
Microsoft 365 Admin Center Steps:
- Go to Azure Active Directory > Security > Conditional Access.
- Create a new policy enforcing MFA for high-risk logins.
Monitor Suspicious Sign-ins with Azure AD Identity Protection
Enable risk-based policies to detect anomalies.
Azure CLI Command:
az ad sp create-for-rbac --name "SecurityMonitoringApp" --role "Security Reader"
4. Disable Legacy Authentication Protocols
Attackers exploit older protocols like IMAP, POP3, and SMTP.
PowerShell Command:
Set-CasMailbox -Identity [email protected] -ImapEnabled $false -PopEnabled $false
5. Use Advanced Anti-Phishing Policies
Configure Microsoft Defender for Office 365 to detect AiTM attacks.
Microsoft 365 Security Command:
New-AntiPhishPolicy -Name "StrictAiTMPolicy" -EnableTargetedUserProtection $true
6. Train Users with Simulated Phishing Campaigns
Use Microsoft Attack Simulator to test employee awareness.
Command to Launch Simulation:
Start-M365DSCPhishingSimulation -TemplateName "AiTM_Phishing_Test"
7. Enable Network-Based Protections
Restrict logins to trusted IPs using Named Locations in Azure AD.
PowerShell Command:
New-AzureADNamedLocationPolicy -OdataType "#microsoft.graph.ipNamedLocation" -DisplayName "Corporate Network" -IpRanges "192.168.1.0/24"
What Undercode Say:
AiTM phishing attacks bypass traditional security layers by intercepting credentials in real time. Defending against them requires a mix of MFA enforcement, Conditional Access, legacy protocol blocking, and user training.
Additional Linux & Windows Commands for Security:
- Check Active Sessions (Linux):
who last
- Audit Failed Logins (Windows):
Get-WinEvent -FilterHashtable @{LogName='Security'; ID=4625} - Block Suspicious IPs (Linux):
iptables -A INPUT -s 1.2.3.4 -j DROP
- Scan for Open Ports (Windows):
Test-NetConnection -ComputerName target.com -Port 443
Stay vigilant, automate threat detection, and continuously update security policies.
Expected Output:
A hardened Microsoft 365 environment resilient against AiTM phishing attacks, with enforced MFA, disabled legacy auth, and real-time monitoring.
🔗 Further Reading: Microsoft Security Best Practices
References:
Reported By: Vand3rlinden Microsoft – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
