One survey noted that individuals from within commit 80% of all computer- and Internet-related crimes against corporations. If so why employees are the highest threat to the security for inappropriate use of IT?
In my view, it depends! If an organization has a state-of-art IT infrastructure, cyber crimes go down to a lot of extent. However, yes! employees are a source of threat to IT security if not trained properly.
I would say unqualified yes to the question. A company without any employees will have fewer problems. However, without employees there will be no one there to fix a problem that does occur. As the company gains in size, it becomes a bigger target.
Employees are the biggest threat because they are already inside the system. Proper training can help. Happy employees can also help as there is less incentive to be deliberately destructive.
Yes, but what makes leaks? You could try and argue that a computer spontaneously leaks information, but I personally suspect that the problem is at the keyboard: by design or by accident. However I am old school where computers were not self-aware. If (or when) that changes then my answer may change as well.
There was a science fiction writer Fredric Brown who wrote a number of short stories. One went something like this: The scientists hooked all the computers from all the worlds together into one large computer. They pushed the switch to finish the link. Their first question was "Is there a god?" The computer answered "There is now." They tried to pull the plug, but a lightning bolt came from a clear blue sky frying the scientist and welding the connection.