A police officer was logging in from his personal computer to the police department's domain server, through remote desktop, to check his email. This was due to his misunderstanding of technology.
A cyber attacker was able to gain access to a city's server through the mayor's home computer, which had been compromised through a phishing email scam. The attacker then logged into the police department's computer to obtain further information.
A good practice in IT security is to give users the least privilege necessary and only for a short duration, as this limits what an attacker can do. Administrators should use their admin accounts only for admin tasks, and not for regular use.