Define risk from network/OS system prospective? And give some risk examples?

Overiew of IT Security Policy Framework

Chain Link Consulting is an IT consulting firm that specializes in system security issues. The company’s president has asked you to help her put together a presentation to a group of potential clients at a trade show meeting next month. First, she wants you to review system security issues, considering all six security levels. Then she wants you to come up with a list of ways that Chain Link could test a client’s security practices, in order to get a real-world assessment of vulnerability. To make matters more interesting, she told you it was OK to be creative in your recommendations, but not to propose any action that would be illegal or unethical. For example, it would be OK to pose as a job applicant with false references to see if they were being checked, but it would not be appropriate to pick a lock and enter the computer room. Your report is due tomorrow. What will you suggest? Explain your answer thoroughly and explain well.

Network and operating system risk definitions? What real-world risks exist?