Rootkit: A type of malicious software designed to gain privileged access to a computer or network, often by masking its existence or operating in stealth mode to evade detection. Rootkits can intercept and change system operations, creating a backdoor for continued access, altering log files, and more. They're notoriously difficult to detect and remove, presenting a significant threat to system integrity.

Root of trust: A set of functions in the trusted computing base with properties that let them be trusted. The Root of Trust serves as a foundation for other system components, ensuring that the hardware, firmware, and software loaded on the system are authentic, unaltered, and, therefore, trustworthy. It is a critical concept in security design to establish a chain of trust, where each component of a system can be validated and trusted based on this root. A root of trust can benefit from Trusted Platform Modules (TPM), Hardware Security Modules (HSM), and root certificate authority servers.

Rotation of duties: A strategy employed to reduce the risk of fraud, errors, and misuse within an organization. It involves periodically rotating employees through different positions and responsibilities to disrupt any actions that might lead to unauthorized or malicious activity. This process helps identify irregularities, provides cross-training opportunities, and ensures no single individual holds a specific responsibility or power for an extended period.

Rounds (in block ciphers): The process or sequence of encryption operations that transforms plaintext into ciphertext and vice versa. Multiple rounds increase the complexity of the encryption and make it more difficult for an unauthorized entity to reverse-engineer the original message. The number of rounds varies depending on the specific encryption algorithm in use.

Routed Protocols: Protocols responsible for carrying user data across networks. These protocols encapsulate the data and ensure it is transmitted across different networks. Examples of routed protocols include Internet Protocol (IP) and Internetwork Packet Exchange (IPX). They rely on routing protocols to determine the path the data should take across networks. These should not be confused with routing protocols like OSPF or BGP.

Router: A networking device that connects multiple networks and forwards data packets between them. It is used to connect different devices and networks, allowing them to communicate with each other. Examples include a home router that connects a local network to the internet or a corporate router that connects multiple office locations.