eplisp

AutoCAD LISP Security Warning: SECURELOAD and Trusted Locations

Stop the LISP loading prompt by adding a trusted location instead of turning security off.

Why the warning appears

If a window titled "Security - Unsigned Executable File" pops up when you load a .lsp file, you are seeing the AutoCAD LISP security warning. AutoCAD asks for confirmation whenever code is about to run from a folder that is not marked as trusted.

The warning does not mean the file is harmful. It only means AutoCAD does not recognize its location. The goal is to keep malicious LISP files that arrive with drawings, or get dropped into support folders, from running without you knowing.

What to choose in the dialog

If you downloaded the file yourself and trust where it came from, choose Load Once. If you do not recognize the file, choose Do Not Load.

If the prompt keeps coming back, the lasting fix is to add the file's folder as a trusted location.

The SECURELOAD system variable

The SECURELOAD system variable controls this behavior. Type SECURELOAD at the command line to see or change its value.

  • 1 (default): files outside trusted locations trigger a warning.
  • 2: only files in trusted locations load; others are blocked without a prompt.
  • 0: no security check; every file loads without a warning.

Adding a Trusted Location

The recommended approach is to keep your LISP files in one folder and make that folder trusted.

  • Type OPTIONS (or OP) at the command line.
  • Open the Files tab and expand Trusted Locations.
  • Click Add, then Browse, and pick the folder (for example C:\eplisp).
  • If the folder is not read-only, AutoCAD shows a security notice; confirm it if you trust the folder.
  • Click Apply and OK.

Using TRUSTEDPATHS from the command line

The same list is stored in the TRUSTEDPATHS system variable. Separate folders with semicolons, and add \... to the end of a path to include its subfolders. Setting the variable replaces the whole list, so read the current value first and append your folder to it.

C:\eplisp;C:\Projects\lisp\...

Why not set SECURELOAD to 0

Setting SECURELOAD to 0 removes the warning, but it also switches the protection off completely. Any LISP file in a received drawing's folder or on your support path could then run without asking.

AutoCAD viruses spread through files named acad.lsp and acaddoc.lsp have used exactly this route in the past. Adding a trusted location is the safe way to get rid of the prompt; turning security off permanently is not.