Files like these are frequently bundled with "trojans." Once executed, they can install background processes that steal passwords, log keystrokes, or encrypt your files for ransom. Anti-virus software often flags these files as "HackTool" or "Trojan," and while some users dismiss these as "false positives," the risk of actual infection is extremely high.
For occasional users, Autodesk offers a "Flex" plan where you purchase tokens and pay only for the days you actually use the software. You can explore these options on the Autodesk Pricing Page. xf-adsk2018-x64
If the cost is a barrier, consider powerful open-source alternatives like Blender (for 3D modeling) or FreeCAD (for parametric 3D modeling), which are entirely free and legal to use for any purpose. Files like these are frequently bundled with "trojans