VLX is a compiler, which can only be loaded with CAD command: appload, and FAS format is also used for loading, so it cannot be viewed. Because it will be garbled when opened.

Create a copy of the acad.vlx file under the help folder (for example, c: \ program files \ AutoCAD 2010 \ help \ logo.gif). Many other files will also be modified, and the value of the ACADLSPASDOC system variable will be changed to 1, which will allow the acad.vlx file to be loaded into other open drawings, thus causing the drawings to be damaged.

By default, AutoCAD software automatically runs files. As long as the file exists in the directory of drawings opened by acad software, it will be automatically executed, which has always been a common way for cad secondary development software to automatically load. When the file exists in some acad working directories or acad program directories, the acad software will also be automatically loaded. Now it is basically a form of CAD virus except for a few secondary development software.