Remote Management and Monitoring tool - DWService - File Signature

Hunt Hypothesis

The hypothesis is that an adversary is leveraging the DWService component of a Remote Management and Monitoring tool to establish persistence or command and control by modifying or replacing file signatures. SOC teams should proactively hunt for this behavior in Azure Sentinel to detect potential adversary use of legitimate RMM tools for covert operations.

KQL Query

let Time_start = now(-5d);
let Time_end = now();
//
DeviceFileCertificateInfo
| where Timestamp between (Time_start..Time_end)
| where Signer has 'DWSNET OÜ'
| summarize FirstSeen=min(Timestamp), LastSeen=max(Timestamp), 
    Report=make_set(ReportId), Count=count() by DeviceId, DeviceName

Analytic Rule Definition

id: 642b39b7-18eb-46eb-ba1f-bf70befae05e
name: Remote Management and Monitoring tool - DWService - File Signature
description: |
    Remote Monitoring and Management (RMM) programs are IT to manage remote endpoints. Attackers have begun to abuse these programs to persist or provide C2 channels.
    https://github.com/jischell-msft/RemoteManagementMonitoringTools
requiredDataConnectors:
- connectorId: MicrosoftThreatProtection
  dataTypes:
  - DeviceFileCertificateInfo
tactics: CommandAndControl
relevantTechniques: T1219
query: |
  let Time_start = now(-5d);
  let Time_end = now();
  //
  DeviceFileCertificateInfo
  | where Timestamp between (Time_start..Time_end)
  | where Signer has 'DWSNET OÜ'
  | summarize FirstSeen=min(Timestamp), LastSeen=max(Timestamp), 
      Report=make_set(ReportId), Count=count() by DeviceId, DeviceName

MITRE ATT&CK Context

• Tactic: CommandAndControl
• Technique: T1219 — T1219

References

• [Source Query](https://github.com/Azure/Azure-Sentinel/blob/main/Hunting Queries/Microsoft 365 Defender/RemoteManagementMonitoring/rmm_DWService_filesig.yaml)

False Positive Guidance

• Scenario: A system administrator is using Dell Command | Configure to deploy a legitimate configuration update to multiple endpoints.
  Filter/Exclusion: Exclude processes initiated by the Dell Command | Configure service or signed by Dell Software.

• Scenario: A scheduled job runs Dell Remote Access Controller (DRAC) to monitor server health and send alerts to the IT team.
  Filter/Exclusion: Exclude traffic from the DRAC IP range or processes with the DRAC service name.

• Scenario: An admin is using Microsoft Intune to push a file signature update to endpoint devices, which triggers the file signature check.
  Filter/Exclusion: Exclude processes initiated by Microsoft Intune or signed by Microsoft Corporation.

• Scenario: A backup job uses Dell Data Protection | Agent to transfer encrypted backup files, which may trigger file signature checks.
  Filter/Exclusion: Exclude processes associated with Dell Data Protection or signed by Dell Technologies.

• Scenario: A user is manually running a Dell SupportAssist scan to check for system issues, which may involve file signature verification.
  Filter/Exclusion: Exclude processes initiated by SupportAssist or signed by Dell SupportAssist.