You have a Microsoft 365 subscription that uses Microsoft Defender for Endpoint Plan Z and...

In Microsoft Defender for Endpoint (MDE) live response sessions, to execute a PowerShell or other script on a remote device, the file must first be uploaded to the device from your local session. Microsoft documentation specifies that the putfile command is used to transfer a file (such as a script, tool, or executable) from the analyst’s workstation to the target device’s temporary working directory for execution.

Even though Script1.ps1 is digitally signed, Defender for Endpoint live response does not automatically access files from local storage or network paths. The analyst must explicitly upload the script using putfile, after which it can be executed within the live response shell.

The library and upload to library commands are used for storing reusable scripts centrally in the Microsoft Defender portal, but that’s not required for a single manual session. Modifying the PowerShell execution policy is unnecessary because MDE live response sessions already allow executing approved scripts.

Hence, to minimize administrative effort and successfully run Script1.ps1 in the live session, the correct first action is:

B. Run the putfile command.