You're probably using the OpenSSH software package. The OpenSSH
scp utility doesn't log anything. It supports debugging output for the underlying SSH session, but that won't log the actual file transfers which are taking place.
Similarly, the OpenSSH server can be set to log detail about what it's doing, and it can be set to log the fact that a user connected and ran
scp, but it won't log the actual file transfers which are taking place.
If you can't get these users to use SFTP instead, there are three approaches available to you:
Investigate alternative (in other words, commercial) SSH/SFTP/SCP servers. They should generally support logging file transfers.
scp utility on the server with one that logs the data you want. OpenSSH is open source. Someone who knows how to program in C for Unix could download the source and modify it.
scp utility with a "wrapper" that launches the original scp program and monitors what it does. There are debugging tools for Unix which can monitor what another process is doing.
I needed to log
scp transfers once, and I used the third approach. I wrote a Perl script which launched the original scp program under strace. Strace would output the names of files being opened and closed by the scp process. The Perl script parsed the strace output and figured out what files were being transferred.