Mary Scott has a master’s degree in computer science and experience as a network engineer. For the past two years, however, she has worked for Hoffman Inc. as an accounts payable clerk. She did not disclose her technology background on her resume when she applied for the clerk position. Early on, Mary established a reputation as a hardworking, enthusiastic, and reliable employee. She often works late and is dedicated to doing an excellent job. Her late night presence in the company became a common occurrence that was at first appreciated by her boss, and then virtually went unnoticed. While working late, Mary used her computer skills to install a sniffer program on the intranet to capture employee IDs and passwords. With the information  she collected, Mary was able to play many roles and establish herself as a vendor, receiving clerk, cash disbursements clerk, and general ledger clerk. With this authority along with her legitimate role of AP clerk, Mary implemented a vendor fraud scheme, which she has been perpetrating for over a year at a cost of $250,000 to Hoffman Inc.

Required
Describe the controls that could have prevented Mary from perpetrating this fraud.