You should be able to control which filetypes (file extensions) are allowed for copy and paste in the TARGIT Client

Currently the are some limitations on which filetypes are allowed for copy and paste in the TARGIT Designer client. These are described in this article: https://community.targit.com/hc/en-us/articles/13168996401180-Copy-paste-documents-between-client-and-file-system 

You should be able to decide if you want to disallow some of the filetypes that are currently allowed.