Works the same way on my Air. Don't know if its always been that way or not. Don't know why it's an issue because I have to login with my password to even get access to the folder like that.
What other issues are you having that makes you think your Mac is hacked?
Are we talking about a folder or about the startup disk? If I try to change permissions on the startup disk, then I have to click the lock to make a change.
Note to self: DO NOT change the startup disk to no access for everyone. I was able to do that by clicking the lock, and it broke everything (stupid me, LOL). Had to boot from a clone, change the permissions back and run disk first aid. After that it restarted from the SSD but took forever. A second restart brought everything back to normal, phew!