Risk is a vulnerability that could allow loss of confidentiality, integrity, or availability of computer services and where there is a possibility of the vulnerability being exploited. Given that, please respond to the question below:

Which of the following activities might be considered a possible source of threat to a company's network, and why?

1. The daily courier service personnel who drop off and pick up packages.
2. Former employees who left the company because of downsizing.
3. An employee traveling on company business to another city.
4. The building management company which manages the organizations offices has decided to install a fire sprinkler system.