This is the fourth article in our four-part series on information barriers in the hedge fund context. The series aims to help hedge fund managers determine whether they should use information barriers and, if so, how they can establish and enforce such barriers. In particular, this fourth article discusses the role of employee training and compliance surveillance in the maintenance of robust information barriers, and describes four significant challenges faced by hedge fund managers in structuring, implementing and enforcing information barriers. The first article provided an overview of various insider trading controls, including restricted lists, watch lists and information barriers, explaining how they can work together; described four principal benefits available from the use of information barriers; highlighted the types of firms that can benefit most from the implementation of information barriers; and described the types of firms that will find the implementation of information barriers most challenging. The second article discussed the legal and regulatory basis for information barriers and described the building blocks of effective barriers (including the key players, physical components and technological processes). The third article described how a firm can limit access to material nonpublic information within the information barrier control environment and outlined policies and procedures designed to bolster the effectiveness of information barriers.