_fpsd user?

Thanks for the info AndreiD (BR). The use of Activity Monitor was a great idea. I repeated your process and I found exactly the same thing. My iMac is configured with OS 10.12.6 and iTunes 12.7. After restarting my computer, I looked for the "_fpsd" while no applications were running. I could not find it. As soon as I started up iTunes (12.7), the "_fpsd" user appeared. It is associated with the "fpsd" process.

I did a second experiment. I have a MacBook Air which is configured with OS 10.12.3 and iTunes 12.6.0.100. Using Activity Monitor, I looked for the "_fpsd" user and the "fpsd" process. They were not present. I then started iTunes (12.6) and I still could not find the "_fpsd" user or "fpsd" process. I upgraded iTunes to 12.7 (leaving the OS at 10.12.3). When I start up iTunes, the "_fpsd" user and the "fpsd" process appeared. Also when I get info on a folder (⌘I) and I go to change the user privileges on the folder I can now see the "_fpsd" user in the list of users I can assign to the folder - which is the original problem I was concerned about. All of this tells me that the "_fpsd" user and the fpsd process are associated with iTunes 12.7 (in some fashion) and that they are part of the normal Apple eco system. I would not recommend that you delete the "_fpsd" user. I tried this and it makes iTunes (12.7) inoperable. I had to install iTunes to recover. I would surmise that this is a minor bug introduced with the iTunes update to 12.7. My original concern was that I had some malware on my system. For me, that concern has has been alleviated.