My friend asked me for some files that I let him take from my system. I did not see he doing that. Then I was left with a doubt: what extra files or data did he take from my system?

I was thinking is here any application or method which shows what data is copied to which USB (if name available then shows name or otherwise device id) and what data is being copied to Ubuntu machine .
It is some like history of USB and System data. I think this feature exists in KDE

This will really useful in may ways. It provides real time and monitoring utility to monitor USB mass storage devices activities on any machine.