upload flow: why wordpress eliminates special characters in filename?

I’ve some problems in uploading and link to posts file having special characters in filename.
I neew to mantain filename as-is, even if containing special characters like & . – _
Wordpress filters and eliminates this character modifying filename.
Can anyone tell me where a can modify the normail workflow of file uploading in order to avoid modifcation in uploaded filename?
Thanks
Stefano