Hope it will help for Windows 8 too.
Unable to use Ctrl+Alt+Del feature on remote desktop running Vista OS/ Windows 7/ Windows 2008.
Problems to use Ctrl+Alt+Del feature on remote desktops running Vista OS/ Windows 7/ Windows-2008 may occur due to one or more of the following reasons:
User Access Control(UAC) is disabled in the remote machine running
Vista OS/ Windows 7/ Windows 2008.
Secure Attention Sequence(SAS) is disabled in the remote machine
running Vista OS/ Windows 7/ Windows 2008.
Enable UAC in the Remote Desktop running Vista OS/ Windows 7/ Windows 2008
Goto Start → Run → type msconfig. This opens the System
Click on Tools tab.
Locate and Click
on "Enable UAP" or "Enable UAC" option item. This opens a Command
Prompt window that automatically executes and runs certain process
to Enable UAC.
Close the cmd window when done. Also close
Restart the computer for the changes to apply.
Set the Policy :
Execute Gpedit.msc from Run prompt.
Goto "Computer Configuration" -> "Admin Templates" -> "Windows Components" -> "Windows Logon Options"
In Windows LogOn Option , double click "Disable enable software Secure Attention Sequence"
Select "Enable" option and "Services and Ease of Access application"