Advanced multistage attack detection in Microsoft Sentinel

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  Microsoft Sentinel in the Azure portal

Microsoft Sentinel uses Fusion, a correlation engine based on scalable machine learning algorithms, to automatically detect multistage attacks (also known as advanced persistent threats or APT) by identifying combinations of anomalous behaviors and suspicious activities that are observed at various stages of the kill chain. Based on these discoveries, Microsoft Sentinel generates incidents that would otherwise be difficult to catch. These incidents comprise two or more alerts or activities. By design, these incidents are low-volume, high-fidelity, and high-severity.

Customized for your environment, this detection technology not only reduces false positive rates but can also detect attacks with limited or missing information.

Since Fusion correlates multiple signals from various products to detect advanced multistage attacks, successful Fusion detections are presented as Fusion incidents on the Microsoft Sentinel Incidents page and not as alerts, and are stored in the SecurityIncident table in Logs and not in the SecurityAlert table.

Configure Fusion

Fusion is enabled by default in Microsoft Sentinel, as an analytics rule called Advanced multistage attack detection. You can view and change the status of the rule, configure source signals to be included in the Fusion ML model, or exclude specific detection patterns that may not be applicable to your environment from Fusion detection. Learn how to configure the Fusion rule.

Note

Microsoft Sentinel currently uses 30 days of historical data to train the Fusion engine's machine learning algorithms. This data is always encrypted using Microsoft’s keys as it passes through the machine learning pipeline. However, the training data is not encrypted using Customer-Managed Keys (CMK) if you enabled CMK in your Microsoft Sentinel workspace. To opt out of Fusion, navigate to Microsoft Sentinel > Configuration > Analytics > Active rules, right-click on the Advanced Multistage Attack Detection rule, and select Disable.

For Microsoft Sentinel workspaces that are onboarded to the Microsoft Defender portal, Fusion is disabled. Its functionality is replaced by the Microsoft Defender XDR correlation engine.

Fusion for emerging threats

Important

Indicated Fusion detections are currently in PREVIEW. See the Supplemental Terms of Use for Microsoft Azure Previews for additional legal terms that apply to Azure features that are in beta, preview, or otherwise not yet released into general availability.

Microsoft Sentinel is generally available within Microsoft's unified security operations platform in the Microsoft Defender portal. For preview, Microsoft Sentinel is available in the Defender portal without Microsoft Defender XDR or an E5 license. For more information, see Microsoft Sentinel in the Microsoft Defender portal.

Note

For information about feature availability in US Government clouds, see the Microsoft Sentinel tables in Cloud feature availability for US Government customers.

Configure Fusion

Fusion is enabled by default in Microsoft Sentinel, as an analytics rule called Advanced multistage attack detection. You can view and change the status of the rule, configure source signals to be included in the Fusion ML model, or exclude specific detection patterns that might not be applicable to your environment from Fusion detection. Learn how to configure the Fusion rule.

You might want to opt out of Fusion if you've enabled Customer-Managed Keys (CMK) in your workspace. Microsoft Sentinel currently uses 30 days of historical data to train the Fusion engine's machine learning algorithms, and this data is always encrypted using Microsoft’s keys as it passes through the machine learning pipeline. However, the training data is not encrypted using CMK. To opt out of Fusion, disable the Advanced Multistage Attack Detection analytics rule in Microsoft Sentinel. For more information, see Configure Fusion rules.

Fusion is disabled in Microsoft Sentinel workspaces that are onboarded to Microsoft's unified security operations (SecOps) platform in the Microsoft Defender portal. Instead, when working with Microsoft's unified SecOps platform, functionality provided by Fusion is replaced by the Microsoft Defender XDR correlation engine.

Fusion for emerging threats (Preview)

The volume of security events continues to grow, and the scope and sophistication of attacks are ever increasing. We can define the known attack scenarios, but how about the emerging and unknown threats in your environment?

Microsoft Sentinel's ML-powered Fusion engine can help you find the emerging and unknown threats in your environment by applying extended ML analysis and by correlating a broader scope of anomalous signals, while keeping the alert fatigue low.

The Fusion engine's ML algorithms constantly learn from existing attacks and apply analysis based on how security analysts think. It can therefore discover previously undetected threats from millions of anomalous behaviors across the kill-chain throughout your environment, which helps you stay one step ahead of the attackers.

Fusion for emerging threats supports data collection and analysis from the following sources:

• Out-of-the-box anomaly detections

• Alerts from Microsoft services:

  • Microsoft Entra ID Protection
  • Microsoft Defender for Cloud
  • Microsoft Defender for IoT
  • Microsoft Defender XDR
  • Microsoft Defender for Cloud Apps
  • Microsoft Defender for Endpoint
  • Microsoft Defender for Identity
  • Microsoft Defender for Office 365

• Alerts from scheduled analytics rules. Analytics rules must contain kill-chain (tactics) and entity mapping information in order to be used by Fusion.

You don't need to have connected all the data sources listed above in order to make Fusion for emerging threats work. However, the more data sources you have connected, the broader the coverage, and the more threats Fusion will find.

When the Fusion engine's correlations result in the detection of an emerging threat, Microsoft Sentinel generates a high-severity incident titled Possible multistage attack activities detected by Fusion.

Fusion for ransomware

Microsoft Sentinel's Fusion engine generates an incident when it detects multiple alerts of different types from the following data sources, and determines that they might be related to ransomware activity:

• Microsoft Defender for Cloud
• Microsoft Defender for Endpoint
• Microsoft Defender for Identity connector
• Microsoft Defender for Cloud Apps
• Microsoft Sentinel scheduled analytics rules. Fusion only considers scheduled analytics rules with tactics information and mapped entities.

Such Fusion incidents are named Multiple alerts possibly related to Ransomware activity detected, and are generated when relevant alerts are detected during a specific time-frame and are associated with the Execution and Defense Evasion stages of an attack.

For example, Microsoft Sentinel would generate an incident for possible ransomware activities if the following alerts are triggered on the same host within a specific timeframe:

Alert	Source	Severity
Windows Error and Warning Events	Microsoft Sentinel scheduled analytics rules	informational
'GandCrab' ransomware was prevented	Microsoft Defender for Cloud	medium
'Emotet' malware was detected	Microsoft Defender for Endpoint	informational
'Tofsee' backdoor was detected	Microsoft Defender for Cloud	low
'Parite' malware was detected	Microsoft Defender for Endpoint	informational

Scenario-based Fusion detections

The following section lists the types of scenario-based multistage attacks, grouped by threat classification, that Microsoft Sentinel detects using the Fusion correlation engine.

In order to enable these Fusion-powered attack detection scenarios, their associated data sources must be ingested to your Log Analytics workspace. Select the links in the table below to learn about each scenario and its associated data sources.

Threat classification	Scenarios
Compute resource abuse	(PREVIEW) Multiple VM creation activities following suspicious Microsoft Entra sign-in
Credential access	(PREVIEW) Multiple passwords reset by user following suspicious sign-in (PREVIEW) Suspicious sign-in coinciding with successful sign-in to Palo Alto VPN by IP with multiple failed Microsoft Entra sign-ins
Credential harvesting	Malicious credential theft tool execution following suspicious sign-in Suspected credential theft activity following suspicious sign-in
Crypto-mining	Crypto-mining activity following suspicious sign-in
Data destruction	Mass file deletion following suspicious Microsoft Entra sign-in (PREVIEW) Mass file deletion following successful Microsoft Entra sign-in from IP blocked by a Cisco firewall appliance (PREVIEW) Mass file deletion following successful sign-in to Palo Alto VPN by IP with multiple failed Microsoft Entra sign-ins (PREVIEW) Suspicious email deletion activity following suspicious Microsoft Entra sign-in
Data exfiltration	(PREVIEW) Mail forwarding activities following new admin-account activity not seen recently Mass file download following suspicious Microsoft Entra sign-in (PREVIEW) Mass file download following successful Microsoft Entra sign-in from IP blocked by a Cisco firewall appliance (PREVIEW) Mass file download coinciding with SharePoint file operation from previously unseen IP Mass file sharing following suspicious Microsoft Entra sign-in (PREVIEW) Multiple Power BI report sharing activities following suspicious Microsoft Entra sign-in Office 365 mailbox exfiltration following a suspicious Microsoft Entra sign-in (PREVIEW) SharePoint file operation from previously unseen IP following malware detection (PREVIEW) Suspicious inbox manipulation rules set following suspicious Microsoft Entra sign-in (PREVIEW) Suspicious Power BI report sharing following suspicious Microsoft Entra sign-in
Denial of service	(PREVIEW) Multiple VM deletion activities following suspicious Microsoft Entra sign-in
Lateral movement	Office 365 impersonation following suspicious Microsoft Entra sign-in (PREVIEW) Suspicious inbox manipulation rules set following suspicious Microsoft Entra sign-in
Malicious administrative activity	Suspicious cloud app administrative activity following suspicious Microsoft Entra sign-in (PREVIEW) Mail forwarding activities following new admin-account activity not seen recently
Malicious execution with legitimate process	(PREVIEW) PowerShell made a suspicious network connection, followed by anomalous traffic flagged by Palo Alto Networks firewall (PREVIEW) Suspicious remote WMI execution followed by anomalous traffic flagged by Palo Alto Networks firewall Suspicious PowerShell command line following suspicious sign-in
Malware C2 or download	(PREVIEW) Beacon pattern detected by Fortinet following multiple failed user sign-ins to a service (PREVIEW) Beacon pattern detected by Fortinet following suspicious Microsoft Entra sign-in (PREVIEW) Network request to TOR anonymization service followed by anomalous traffic flagged by Palo Alto Networks firewall (PREVIEW) Outbound connection to IP with a history of unauthorized access attempts followed by anomalous traffic flagged by Palo Alto Networks firewall
Persistence	(PREVIEW) Rare application consent following suspicious sign-in
Ransomware	Ransomware execution following suspicious Microsoft Entra sign-in
Remote exploitation	(PREVIEW) Suspected use of attack framework followed by anomalous traffic flagged by Palo Alto Networks firewall
Resource hijacking	(PREVIEW) Suspicious resource / resource group deployment by a previously unseen caller following suspicious Microsoft Entra sign-in

Related content

For more information, see:

• Scenarios detected by the Microsoft Sentinel Fusion engine
• Configure multistage attack detection (Fusion) rules in Microsoft Sentinel