How to detect if a running Windows application is being accessed remotely?

There is a Win32 API that is designed for this:

GetSystemMetrics(SM_REMOTESESSION);

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When the program running in a remote desktop session the API will return not zero value.
Please check this web-site how to call this API via PInvoke:

Public Declare Auto Function GetSystemMetrics Lib "user32.dll" (ByVal smIndex As Integer) As Integer

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Hi samirbhogayta,  thanks for your suggestion.

I am not a c## developer, so I converted your code to vb.net:

Imports System.Runtime.InteropServices

Public Class RemoteSessionChecker
	''' <summary>
	''' Checks whether the current user is is logged in through a remote session
	''' </summary>
	''' <returns></returns>
	Public Shared Function Check() As Boolean
		Dim IsRemoteSession As Boolean = False
		'Constant used to check for remote sessions
		Const  SM_REMOTESESSION As Integer = &H2001
		'This function will return 0 if the session is local
		Dim Value As Integer = GetSystemMetrics(SM_REMOTESESSION)

		IsRemoteSession = (Value <> 0)

		Return IsRemoteSession
	End Function

	<DllImport("user32.dll", EntryPoint := ("GetSystemMetrics"))> _
	Private Shared Function GetSystemMetrics(nIndex As Integer) As Integer
	End Function
End Class

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But the function always returns False - even when I am connected by RDP.

Regards,
Leigh

Thanks, chaau.

Changing SM_REMOTESESSION value (for VB) to &H1000 now makes the code detect if it is connected by RDP.
That's the good news.

The bad news is that it does not detect if it is connected via TeamViewer.  (I haven't tried VNC or anything else).

Teamviewer, Logmein and such technically do not work via RDP, but connect to the user session. They cannot be detected via SM_REMOTESESSION. You will need to test if processes associated with these services are running using CreateToolhelp32Snapshot() API.