A couple days ago I found out whenever I'm out of the office (meetings, vacation, etc), that one of my coworkers have straight up been using my work computer in addition to their own work computer before logging off and putting everything back to normal before I'm back. I asked them about it and they said that it was okay because they logged into their own account and it is a company computer. That's true I technically don't own the computer but it's the one assigned to me so isn't it expected that others don't use it, especially so secretively? They won't tell me what they're even using it for (though it's probably non-work stuff...) and I am honestly shocked that this has just been going on without me knowing at all. Shouldn't they ask my permission to use my computer first, or is this acceptable behaviour since it's a company computer and they use their account?