Recently I answered a forum question at another site that asked "How do I get root's environment with sudo su". I answered "sudo su -", and seconds later someone else opined "Sure, if you want to completely destroy your security".
Well, yeah. Except that he'd already done that by allowing "su" in sudoers, so adding the "-" isn't the problem. It's also pretty obvious that allowing "su" to a sudo user works on the honor system. Any person given that privilege could subvert the intention (logging of usage) easily.
It's a convenience, though. The real admin can grant temporary privilege to
someone like me without actually changing the password. Assuming they trust me not to be up to no good, they have a record of my use of that privilege. It's only
marginally more convenient than handing me the password or temporarily changing the password, but that margin is present, so people do this, and not just for passing consultants: full time admins often have this power but don't have "root".
Well, we all know that the road to computer hell is paved with convenience. Microsoft has shown us that and plenty of sloppy Unix programmers have kicked in their own fair share. Convenience always lessens security.
The person who carped about security mentioned Slackware, noting that
at least there, sudoers would never have a default configuration that included "su".
Bully for Slackware, I say, but let's not pretend that is the be all and end all of security. Truly secure systems have no all powerful root user at all and people who need such systems understand why such a user is a bad idea. It's why a safe deposit vault needs two keys - one user with unlimited power can obviously subvert a system. Truly secure systems (computer or not) are carefully planned so that audits are always in place and can never be bypassed.
But using such a system in most business environments would be insane. The root user is a point of weakness, but it is also a great convenience.