Application whitelisting is a security approach that allows only pre-approved applications to execute within a system or network. This method operates on a 'default deny' principle, meaning if an application is not explicitly listed as approved, it will not be allowed to run. This is in contrast to application blacklisting, which operates on a 'default allow' principle where all applications are allowed to run unless they have been specifically identified as malicious or undesirable and added to a blacklist. Whitelisting is generally considered more secure because it prevents any unapproved applications from running, which can include new or unknown threats. However, it can be more challenging to maintain as it requires a comprehensive understanding of all the necessary applications for business operations.

The transport layer ensures that messages are delivered in the order in which they are sent and that there is no loss or duplication. Transport layer maintains data integrity. Answer option C is incorrect. The Internet Layer of the TCP/IP model solves the problem of sending packets across one or more networks. Internetworking requires sending data from the source network to the destination network. This process is called routing. IP can carry data for a number of different upper layer protocols. Answer option B is incorrect. The Link Layer of TCP/IP model is the networking scope of the local network connection to which a host is attached. This is the lowest component layer of the Internet protocols, as TCP/IP is designed to be hardware independent. As a result TCP/IP has been implemented on top of virtually any hardware networking technology in existence. The Link Layer is used to move packets between the Internet Layer interfaces of two different hosts on the same link. The processes of transmitting and receiving packets on a given link can be controlled both in the software device driver for the network card, as well as on firmware or specialized chipsets. Answer option D is incorrect. The Application Layer of TCP/IP model refers to the higher-level protocols used by most applications for network communication. Examples of application layer protocols include the File Transfer Protocol (FTP) and the Simple Mail Transfer Protocol (SMTP). Data coded according to application layer protocols are then encapsulated into one or more transport layer protocols, which in turn use lower layer protocols to affect actual data transfer.

To restore the registry on a Windows-based network, a system administrator can utilize several utilities. The Reg.exe utility is a command-line tool that allows for manipulation of the Windows registry from the command prompt, including the ability to restore it1Regedit.exe is another utility that provides a graphical interface for users to view and modify the registry2. Both these tools are capable of restoring the registry to a previous state if changes have been made that affect system performance or stability.