How to make my `/usr` folder secure? I'm trying to install the Tunnelblick open source VPN client on my Mac running OS X 10.10.5. 

When I try to install the dmg I get the following error (see attached screenshot). 



How would I make my /usr folder secure? The account I use by default is my main user account, but also the admin account for the computer. Would it be a question of making a my main user account a standard user and setting up a separate admin account?
It seems the permissions on /usr are incorrect, which in the past has been attributed to installing MacPorts. You can repair the permissions on /usr by running:

sudo chown root:wheel /usr
sudo chmod 0755 /usr


Since MacPorts installs to /opt/local, this shouldn't affect MacPorts, but as I don't use MacPorts I can't say for certain.