🔹 Introduction
In today’s rapidly evolving cybersecurity landscape, organizations face constant threats from malware, phishing, ransomware, and advanced persistent attacks. Microsoft Defender provides a centralized security solution that enables IT and security professionals to detect, investigate, and respond to security incidents effectively.
This blog covers:
✅ What Microsoft Defender Incident & Alerts Are
✅ How Microsoft Defender Detects & Classifies Threats
✅ How to Investigate & Respond to Alerts
✅ Automating Incident Response with PowerShell
✅ Best Practices for Proactive Security
🔹 What Are Microsoft Defender Incidents & Alerts?
Microsoft Defender uses AI-driven threat detection to identify and categorize security threats within an organization.
🔸 What Is an Incident?
An incident is a collection of related security alerts grouped into a single case. It represents a potential breach, helping security teams focus on a broader attack pattern rather than isolated alerts.
🔸 What Is an Alert?
An alert is a single security event triggered by Microsoft Defender for Endpoint, Microsoft Defender for Office 365, or Microsoft Defender for Identity when suspicious activity is detected.
👉 Example Alerts:
🔹 A user clicked on a phishing link in an email
🔹 A process executed malicious PowerShell commands
🔹 An unauthorized login attempt was made from a foreign IP
🔹 How Microsoft Defender Detects & Classifies Threats
Microsoft Defender correlates signals from endpoints, email, identity, and cloud applications to detect and classify threats into different severity levels:
| Severity | Description |
|---|---|
| High | Active malware/ransomware, active exploitation of vulnerabilities |
| Medium | Suspicious activity, potential phishing, or initial exploitation attempts |
| Low | Anomalies that may indicate reconnaissance or minor policy violations |
| Informational | Non-malicious unusual activity, failed login attempts, etc. |
🔹 Investigating & Responding to Defender Alerts
Step 1: View Security Incidents in the Microsoft Defender Portal
1️⃣ Go to: Microsoft Defender Security Portal
2️⃣ Navigate to: Incidents & Alerts
3️⃣ Click on an Incident to view related alerts, affected assets, and recommendations
Step 2: Investigate Suspicious Activity
🔹 Check Alert Details (Time, Device, User, Process Executed)
🔹 View Process Tree Analysis to understand malware execution
🔹 Analyze Network Connections for suspicious IPs
Step 3: Take Remediation Actions
✅ Isolate a Compromised Device
powershellCopyEditInvoke-DeviceIsolation -DeviceId "DeviceID123" -IsolationType "Full"
✅ Run an Antivirus Scan on an Affected Machine
powershellCopyEditStart-MpScan -ScanType FullScan
✅ Block a Malicious URL Using Defender
powershellCopyEditAdd-MpPreference -AttackSurfaceReductionRules_Ids "D1E49AAC-8F56-4280-B9BA-993A6D77406C" -AttackSurfaceReductionRules_Actions Enabled
✅ Disable a Compromised User Account
powershellCopyEditDisable-AzureADUser -ObjectId "UserObjectID"
🔹 Automating Incident Response with PowerShell
Security teams can automate incident detection and response using Microsoft Graph Security API and PowerShell.
List All Security Incidents
powershellCopyEditConnect-MgGraph -Scopes SecurityEvents.Read.All
Get-MgSecurityIncident
Get Details of a Specific Incident
powershellCopyEdit$IncidentId = "<incidentID>"
Get-MgSecurityIncident -IncidentId $IncidentId
Resolve an Incident
powershellCopyEditUpdate-MgSecurityIncident -IncidentId $IncidentId -Status "Resolved"
🔹 Best Practices for Microsoft Defender Security Monitoring
✔ Enable Defender XDR (Extended Detection & Response) to correlate threats across email, endpoints, and identity.
✔ Use Automated Investigation & Response (AIR) to automatically contain threats.
✔ Set up Security Playbooks in Microsoft Sentinel for automated incident handling.
✔ Enable Threat Intelligence Integration to detect nation-state or advanced threats.
✔ Regularly review & tune alert policies to reduce false positives.
✅ Conclusion
Microsoft Defender provides real-time threat intelligence, automated incident response, and deep security insights to proactively protect organizations. By leveraging PowerShell, automation, and best practices, IT security teams can efficiently detect, investigate, and remediate security incidents.
🚀 Next Steps:
🔹 Set up Conditional Access Policies to block risky sign-ins
🔹 Integrate Microsoft Defender with Microsoft Sentinel for better threat visibility
🔹 Automate threat response workflows using Power Automate & Security Playbooks
💬 Have you encountered any security incidents recently? Share your experiences below!