Remote Management and Monitoring tool - TightVNC - Network Connection

Hunt Hypothesis

The detection identifies potential adversary use of TightVNC for remote management and command and control activities, leveraging its network connection capabilities for persistence or exfiltration. SOC teams should proactively hunt for this behavior in Azure Sentinel to identify and mitigate potential compromise of endpoints through abused RMM tools.

KQL Query

let Time_start = now(-5d);
let Time_end = now();
//
DeviceNetworkEvents
| where Timestamp between (Time_start..Time_end)
| where InitiatingProcessVersionInfoCompanyName has 'GlavSoft'
    and InitiatingProcessVersionInfoProductName has 'TightVNC'
| summarize FirstSeen=min(Timestamp), LastSeen=max(Timestamp), 
    Report=make_set(ReportId), Count=count() by DeviceId, DeviceName,
    RemoteUrl 

Analytic Rule Definition

id: 4323b279-4600-4fc6-a0b9-1d8d678c6b1b
name: Remote Management and Monitoring tool - TightVNC - Network Connection
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:
  - DeviceNetworkEvents
tactics: CommandAndControl
relevantTechniques: T1219
query: |
  let Time_start = now(-5d);
  let Time_end = now();
  //
  DeviceNetworkEvents
  | where Timestamp between (Time_start..Time_end)
  | where InitiatingProcessVersionInfoCompanyName has 'GlavSoft'
      and InitiatingProcessVersionInfoProductName has 'TightVNC'
  | summarize FirstSeen=min(Timestamp), LastSeen=max(Timestamp), 
      Report=make_set(ReportId), Count=count() by DeviceId, DeviceName,
      RemoteUrl 

Required Data Sources

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_netconn.yaml)

False Positive Guidance

• Scenario: Scheduled Maintenance Task Using TightVNC
  Description: An administrator schedules a routine maintenance task using TightVNC to remotely reboot a server or apply patches.
  Filter/Exclusion: process.name != "tvncviewer.exe" OR process.name != "tvncserver.exe" OR (process.name == "tvncviewer.exe" AND event_id == 41)

• Scenario: Remote Desktop Session via TightVNC
  Description: A legitimate remote desktop session is established using TightVNC for user support or troubleshooting.
  Filter/Exclusion: process.name != "tvncviewer.exe" OR (process.name == "tvncviewer.exe" AND destination_ip IN (list_of_known_admin_ips))

• Scenario: TightVNC Used for System Monitoring by IT Team
  Description: The IT team uses TightVNC to monitor system performance and collect logs from remote endpoints.
  Filter/Exclusion: process.name != "tvncviewer.exe" OR (process.name == "tvncviewer.exe" AND user_account IN (list_of_it_admin_accounts))

• Scenario: TightVNC Used for Software Deployment
  Description: A deployment tool uses TightVNC to push updates or configurations to multiple endpoints during a scheduled deployment.
  Filter/Exclusion: process.name != "tvncviewer.exe" OR (process.name == "tvncviewer.exe" AND event_id == 1001)

• Scenario: TightVNC Used for Remote Support by Help Desk
  Description: The help desk uses TightVNC to assist end-users with software issues or configuration changes.
  Filter/Exclusion: process.name != "tvncviewer.exe" OR (process.name == "tvncviewer.exe" AND user_account IN (list_of_helpdesk_accounts))