Remote Management and Monitoring tool - TightVNC - File Signature

Hunt Hypothesis

The detection identifies potential adversary use of TightVNC, a Remote Management and Monitoring tool, to establish persistence or command and control channels by leveraging its file signature. SOC teams should proactively hunt for this behavior in Azure Sentinel to detect and mitigate potential long-term adversary presence and exfiltration activities.

KQL Query

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

Analytic Rule Definition

id: 18f7c17b-65d4-4263-b9e2-587e84233989
name: Remote Management and Monitoring tool - TightVNC - 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 'glavsoft'
  | 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_TightVNC_filesig.yaml)

False Positive Guidance

• Scenario: IT administrators are using TightVNC to perform remote desktop support on endpoint systems.
  Filter/Exclusion: process.name != "tightvnc.exe" or process.parent.name != "tightvnc.exe"

• Scenario: A scheduled job is configured to run a legitimate script via TightVNC to automate system maintenance tasks.
  Filter/Exclusion: process.name != "tightvnc.exe" or process.parent.name != "tightvnc.exe"

• Scenario: An admin is using TightVNC to remotely configure a firewall rule on a server.
  Filter/Exclusion: process.name != "tightvnc.exe" or process.parent.name != "tightvnc.exe"

• Scenario: A legitimate system management tool like Microsoft System Center Configuration Manager (SCCM) is using TightVNC for remote control during patch deployment.
  Filter/Exclusion: process.parent.name != "msiexec.exe" or process.parent.name != "sccm.exe"

• Scenario: A user is using TightVNC to access a virtual desktop infrastructure (VDI) environment for remote work.
  Filter/Exclusion: process.name != "tightvnc.exe" or process.parent.name != "vncviewer.exe"