Urge employees to log off their computer systems when they leave their desks. This will prevent impersonation scams. Imagine that Veronica leaves her desk and doesn't log off. Guess who's name is on the return e-mail address. Verify your large orders and new accounts by phone.
Impersonation can be a be big fraud factor.
You're left holding the losses. Pirate software is software that you didn't pay for, but use anyway. This violates the publisher's rights. If the publisher finds out, you can be sued for hundreds of thousands of dollars. When you let an employee go, change his password immediately, so he can't damage your files if he is vengeful.