Windows RDP Registry Settings Modified to Zero

ATT&CK techniques

Persistence → Defense Evasion

Recon
Resource Dev
Initial Access
Execution
Persistence
- T1112Modify Registry
Priv Esc
Defense Evasion
- T1112Modify Registry
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule flags registry changes to specific Remote Desktop (Terminal Services) settings where the value is set to DWORD 0x00000000. It matters because disabling restrictions or changing authentication/session controls can enable unauthorized remote access or weaken RDP defenses. The detection relies on Windows registry-set telemetry matching targeted value names ending with fDenyTSConnections, fSingleSessionPerUser, and UserAuthentication, and the data value being zero.

Reporting behind it

Related detections9 linkedT1112 — drag to rearrange

Malicious Enabling of Restricted Admin Mode via Registry by UAT-8837

Suspicious Enabling of Remote Desktop via fDenyTSConnections Registry by DeadLock Ransomware

Malicious Service DLL Hijack for Persistence via Lotus Blossom

Suspicious Loopback Proxy Server Configured via Registry (via registry_set)

Malicious WDigest Credential Caching Enabled via Registry (via registry_set)

Suspicious Remote Desktop Enabled via fDenyTSConnections Registry by Sandworm

Malicious Gh0stBins RAT Registry Marker HHClient

Suspicious PebbleDash C2 Configuration Stored Under WMI Security Key (via registry_set)

Suspicious WDigest UseLogonCredential Enablement for Plaintext Credential Theft (via registry_set)

Windows RDP Registry Settings Modified to Zero

Pivot detection · T1112 · 9 related

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.

windows-rdp-registry-settings-modified-to-zero-a2863fbc

title: Windows RDP Registry Settings Modified to Zero
id: 8b19a4bc-a5e2-4e25-99b0-33482484e007
related:
  - id: 3f6b7b62-61aa-45db-96bd-9c31b36b653c
    type: similar
  - id: 4b8f6d3a-9c5e-4f2a-a7d8-6b9c3e5f2a8d
    type: similar
  - id: a2863fbc-d5cb-48d5-83fb-d976d4b1743b
    type: derived
status: test
description: This rule flags registry changes to specific Remote Desktop (Terminal Services) settings where the value is set to DWORD 0x00000000. It matters because disabling restrictions or changing authentication/session controls can enable unauthorized remote access or weaken RDP defenses. The detection relies on Windows registry-set telemetry matching targeted value names ending with fDenyTSConnections, fSingleSessionPerUser, and UserAuthentication, and the data value being zero.
references:
  - https://web.archive.org/web/20200929062532/https://blog.menasec.net/2019/02/threat-hunting-rdp-hijacking-via.html
  - http://woshub.com/rds-shadow-how-to-connect-to-a-user-session-in-windows-server-2012-r2/
  - https://twitter.com/SagieSec/status/1469001618863624194?t=HRf0eA0W1YYzkTSHb-Ky1A&s=03
  - https://threathunterplaybook.com/hunts/windows/190407-RegModEnableRDPConnections/notebook.html
  - https://bazaar.abuse.ch/sample/6f3aa9362d72e806490a8abce245331030d1ab5ac77e400dd475748236a6cc81/
  - http://etutorials.org/Microsoft+Products/microsoft+windows+server+2003+terminal+services/Chapter+6+Registry/Registry+Keys+for+Terminal+Services/
  - https://admx.help/HKLM/SOFTWARE/Policies/Microsoft/Windows%20NT/Terminal%20Services
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/registry/registry_set/registry_set_terminal_server_suspicious.yml
author: Samir Bousseaden, David ANDRE, Roberto Rodriguez @Cyb3rWard0g, Nasreddine Bencherchali, Huntrule Team
date: 2022-09-29
modified: 2022-11-26
tags:
  - attack.persistence
  - attack.defense-impairment
  - attack.t1112
logsource:
  category: registry_set
  product: windows
detection:
  selection:
    TargetObject|endswith:
      - \fDenyTSConnections
      - \fSingleSessionPerUser
      - \UserAuthentication
    Details: DWORD (0x00000000)
  condition: selection
falsepositives:
  - Some of the keys mentioned here could be modified by an administrator while setting group policy (it should be investigated either way)
level: medium
license: DRL-1.1

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