RDP Sensitive Settings Changed to Zero

calendar Aug 12, 2024 · attack.defense-evasion attack.persistence attack.t1112  ·
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Detects tampering of RDP Terminal Service/Server sensitive settings. Such as allowing unauthorized users access to a system via the 'fAllowUnsolicited' or enabling RDP via 'fDenyTSConnections', etc.

Sigma rule (View on GitHub)

 1title: RDP Sensitive Settings Changed to Zero
 2id: a2863fbc-d5cb-48d5-83fb-d976d4b1743b
 3related:
 4    - id: 3f6b7b62-61aa-45db-96bd-9c31b36b653c
 5      type: similar
 6status: test
 7description: |
 8    Detects tampering of RDP Terminal Service/Server sensitive settings.
 9    Such as allowing unauthorized users access to a system via the 'fAllowUnsolicited' or enabling RDP via 'fDenyTSConnections', etc.    
10references:
11    - https://web.archive.org/web/20200929062532/https://blog.menasec.net/2019/02/threat-hunting-rdp-hijacking-via.html # Related to RDP hijacking via the "ServiceDll" key
12    - http://woshub.com/rds-shadow-how-to-connect-to-a-user-session-in-windows-server-2012-r2/ # Related to the Shadow RPD technique
13    - https://twitter.com/SagieSec/status/1469001618863624194?t=HRf0eA0W1YYzkTSHb-Ky1A&s=03 # Related to the Shadow RPD technique
14    - https://threathunterplaybook.com/hunts/windows/190407-RegModEnableRDPConnections/notebook.html
15    - https://bazaar.abuse.ch/sample/6f3aa9362d72e806490a8abce245331030d1ab5ac77e400dd475748236a6cc81/
16    - http://etutorials.org/Microsoft+Products/microsoft+windows+server+2003+terminal+services/Chapter+6+Registry/Registry+Keys+for+Terminal+Services/ # Contain description for most of the keys mentioned here (check it out if you want more information
17    - https://admx.help/HKLM/SOFTWARE/Policies/Microsoft/Windows%20NT/Terminal%20Services # Contain description for most of the keys mentioned here (check it out if you want more information)
18author: Samir Bousseaden, David ANDRE, Roberto Rodriguez @Cyb3rWard0g, Nasreddine Bencherchali
19date: 2022-09-29
20modified: 2022-11-26
21tags:
22    - attack.defense-evasion
23    - attack.persistence
24    - attack.t1112
25logsource:
26    category: registry_set
27    product: windows
28detection:
29    selection:
30        TargetObject|endswith:
31            - '\fDenyTSConnections' # Specifies whether Remote Desktop connections are enabled - When set to zero RDP is enabled
32            - '\fSingleSessionPerUser' # When changed to 0 it allows multiple RDP sessions
33            - '\UserAuthentication' # Specifies that Network-Level user authentication is not required before the remote desktop connection is established
34        Details: 'DWORD (0x00000000)'
35    condition: selection
36falsepositives:
37    - Some of the keys mentioned here could be modified by an administrator while setting group policy (it should be investigated either way)
38level: medium

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