Explanation: Non-repudiation is a term that refers to the ability to ensure that a party to a dispute cannot deny the authenticity of their signature on a document or the sending of a message that they originated. Non-repudiation is the concept of ensuring that a party in a dispute cannot refuse to acknowledge, or refute the validity of a statement or contract. As a service, it provides proof of the integrity and origin of data. Although this concept can be applied to any transmission, including television and radio, by far the most common application is in the verification and trust of signatures. Answer: A is incorrect. Confidentiality is a mechanism that ensures that only the intended and authorized recipients are able to read data. The data is so encrypted that even if an unauthorized user gets access to it, he will not get any meaning out of it. Answer: C is incorrect. Reconnaissance is a term that refers to information gathering behaviors that aim to profile the organization, employees, network, and systems before an attack is performed efficiently. It is the first step in the process of intrusion and involves unauthorized discovery and mapping of systems, services, or vulnerabilities. These discovery and mapping techniques are commonly known as scanning and enumeration. Common tools, commands, and utilities used for scanning and enumeration include ping, telnet, nslookup, rpcinfo, File Explorer, finger, etc. Reconnaissance activities take place before performing a malicious attack. These activities are used to increase the probability of successful operation against the target, and to increase the probability of hiding the attacker’s identity. Answer: B is incorrect. OS fingerprinting is a process in which an external host sends special traffic on the external network interface of a computer to determine the computer’s operating system. It is one of the primary steps taken by hackers in preparing an attack.