Getting "Drawing File is not valid" when opening an old CAD file.

[h_cotta]

I'm trying to access an old CAD file (last modified in 2003) using AutoCAD Map 2008, but I keep getting "Drawing File is not valid".

So far I've tried:

1. Copying the file locally and opening it (it was originally hosted on an on-premise server, and it's now hosted on SharePoint)
2. Opening the file in DWG TrueView (2024);
3. Using the RECOVER and RECOVERALL commands on file (got "File cannot be recovered");
4. Using the INSERT command on a blank document and selecting the problematic file (didn't work);
5. Changing the extension of the BAK file to DWG and repeating steps 2-4 on the new file;
6. Looking for the original file on the decommissioned on-prem server and repeating steps 2-5 on those files;
7. Looking for an SV$ file on the "Windows\Temp" directory on both client and server (as expected, that's long gone by now);

I'm aware that the company suffered ransomware attacks in the past (before my time here) and had files in the server encrypted. I don't know what method they used to recover the files, but I can open other DWG files on both parent and sibling directories, so whatever they did worked well for other files.

[paullimapa]

Unfortunately Not all encrypted files from ransomware can be properly recovered 

[h_cotta]

Yeah, I was hoping this could be a "CAD problem" not related to the file encryption and maybe there was something else I could try. But I think my best bet will be to try and find a copy of the file that wasn't affected by the attack.

[pendean]

Looks like you covered about all that can be done unless you spot something else here https://www.autodesk.com/support/technical/article/caas/sfdcarticles/sfdcarticles/Drawing-file-is-no...