Evaluate alerts and incidents in Microsoft Sentinel

An alert in Sentinel represents a potential security issue that has been identified by the analytics tools within the service. Alerts are generated based on analytics rules that are either pre-defined or custom-made by the security team. These rules can use various data sources, including logs from Azure services, on-premises equipment, and other cloud providers.

Alerts in Microsoft Sentinel have different severity levels:

• Low: Unusual but not necessarily indicative of a security issue.
• Medium: Suggests a potential security issue that may require further investigation.
• High: Indicates a likely security issue that should be investigated immediately.
• Informational: Offers insights into security operations without requiring immediate action.

Processing Incidents in Microsoft Sentinel

An incident in Sentinel is an aggregation of related alerts that may constitute a security threat or breach. When multiple alerts correlate to a particular attack pattern or when a single alert is significant enough, an incident is created.

Incidents are categorized on various factors including:

• Severity: Reflecting the highest severity of associated alerts.
• Status: Indicates whether the incident is active, in progress, or resolved.
• Classification: Shows the nature of the incident, which could be true positive, false positive, benign positive, or undetermined.

Investigation and Response

Upon an alert or incident being triggered, a security analyst will perform an investigation. The investigation aims to determine the scope, impact, and the underlying cause of the incident. Microsoft Sentinel provides tools and features like the investigation graph to visualize relationships between alerts, and entities and to track the trajectory of an attack.

The analyst follows these steps:

1. Review Alert Details: Look at the raw data, entities involved, and the context around the alert.
2. Correlate Information: Use internal and external threat intelligence to enrich the alert and understand its relevance.
3. Determine Impact: Assess which resources are affected and the potential risk to the organization.
4. Containment: If an active threat is identified, take measures to contain it, such as isolating affected systems or revoking compromised credentials.
5. Eradication: Address the root cause of the incident to prevent recurrence.
6. Recovery: Restore systems and data affected by the incident to their normal state.
7. Post-Incident Analysis: Once the threat is neutralized, analyze the incident for lessons learned, improve defensive measures, and update incident response plans.

Automation and Orchestration

Workbooks and playbooks in Microsoft Sentinel can automate responses to certain alerts. These can range from simple notifications to complex remediation tasks.

• Workbooks: Provide templates for visualizing and analyzing data related to security operations.
• Playbooks: Automated, pre-defined procedures that respond to alerts. They are powered by Azure Logic Apps and can perform tasks such as sending an email, creating a ticket, or initiating a workflow in another system.

Microsoft Sentinel allows for automation rules to be set, which can:

• Change the status of an incident.
• Assign ownership of an incident to the appropriate personnel.
• Add tags to an incident for easier categorization or follow-up.

Best Practices for Evaluating Alerts and Incidents

• Regularly review and refine analytics rules to minimize false positives.
• Integrate threat intelligence feeds to enhance the context of alerts and incidents.
• Document and adhere to incident response procedures to ensure consistency and efficiency.
• Utilize user and entity behavior analytics (UEBA) to detect anomalies that could indicate sophisticated attacks.
• Maintain an updated inventory of assets and their criticality to prioritize response efforts.
• Conduct regular drills and exercises to ensure your team is prepared for incident response.

By following a structured approach to evaluate alerts and incidents within Microsoft Sentinel, organizations can effectively combat cybersecurity threats and reduce their overall risk profile. Implementing playbooks for predictable scenarios can save valuable time during an incident response, while investing in training for security personnel can enhance the effectiveness of investigations.