Enable Remote Desktop Conections Registry¶

Metadata¶


collaborators	[‘Roberto Rodriguez @Cyb3rWard0g’, ‘Jose Rodriguez @Cyb3rPandaH’]
creation date	2019/04/07
modification date	2020/09/20
playbook related	[]

Hypothesis¶

Adversaries might be modifying registry key values to enable remote desktop connections in my environment

Technical Context¶

Remote desktop is a common feature in operating systems. It allows a user to log into an interactive session with a system desktop graphical user interface on a remote system. Microsoft refers to its implementation of the Remote Desktop Protocol (RDP) as Remote Desktop Services (RDS).

Offensive Tradecraft¶

Adversaries may connect to a remote system over RDP/RDS to expand access if the service is enabled and allows access to accounts with known credentials. There are several settings that must be configured to enable Remote Desktop connections. First, you must enable Remote Desktop connections by using the fDenyTSConnections setting. Setting fDenyTSConnections=False in the Microsoft-Windows-TerminalServices-LocalSessionManager component (HKLM:\SYSTEM\CurrentControlSet\Control\Terminal Server) specifies whether Remote Desktop connections are enabled.

An adversary can also specify how users are authenticated. Setting UserAuthentication=0 in the Microsoft-Windows-TerminalServices-RDP-WinStationExtensions component (HKLM:\System\CurrentControlSet\Control\Terminal Server\WinStations\RDP-Tcp) helps make sure that users can connect remotely from computers that don’t run Remote Desktop by using network-level authentication. This is the equivalent of Allow connections from computers running any version of Remote Desktop (less secure) security setting.

Mordor Test Data¶


metadata	https://mordordatasets.com/notebooks/small/windows/05_defense_evasion/SDWIN-190518203650.html
link	https://raw.githubusercontent.com/OTRF/mordor/master/datasets/small/windows/defense_evasion/host/empire_enable_rdp.tar.gz

Analytics¶

Initialize Analytics Engine¶

from openhunt.mordorutils import *
spark = get_spark()

Download & Process Mordor Dataset¶

mordor_file = "https://raw.githubusercontent.com/OTRF/mordor/master/datasets/small/windows/defense_evasion/host/empire_enable_rdp.tar.gz"
registerMordorSQLTable(spark, mordor_file, "mordorTable")

Analytic I¶

Look for any process updating fDenyTSConnections or UserAuthentication registry key values

Data source	Event Provider	Relationship	Event
Windows registry	Microsoft-Windows-Sysmon/Operational	Process modified Windows registry key value	13

df = spark.sql(
'''
SELECT `@timestamp`, Hostname, Image, TargetObject
FROM mordorTable
WHERE Channel = "Microsoft-Windows-Sysmon/Operational"
    AND EventID = 13
    AND (TargetObject LIKE "%fDenyTSConnections"
        OR TargetObject LIKE "%UserAuthentication")
    AND Details = "DWORD (0x00000000)"
'''
)
df.show(10,False)

Known Bypasses¶

Idea	Playbook

False Positives¶

None

Hunter Notes¶

if the activity defined above happens frequently in your environment, you cshould Stack the processeses modifying the registry key values.

Hunt Output¶

Type	Link
Sigma Rule	https://github.com/OTRF/ThreatHunter-Playbook/tree/master/signatures/sigma/sysmon_rdp_registry_modification.yml

References¶

https://attack.mitre.org/techniques/T1076/
https://github.com/EmpireProject/Empire/blob/master/lib/modules/powershell/management/enable_rdp.py
https://docs.microsoft.com/en-us/windows-hardware/customize/desktop/unattend/microsoft-windows-terminalservices-localsessionmanager-fdenytsconnections
https://docs.microsoft.com/en-us/windows-hardware/manufacture/desktop/enable-remote-desktop-by-using-an-answer-file

Threat Hunter Playbook