[Exim] system filter for renameing attachments

Hello,

I'am looking for system filter which can rename attachments, for
example: program.exe -> program.exe_

Also it would be nice, if we could place a warning messages into these
emails. Something like:
!! Attachement renamed - Attention: don't execute unknown attachments !!

We use Exim 4.24. Exists there any solution for this problem? Have
someone written a corresponding system filter?

- oliver