Which of the following best describes a 'Trojan horse' in cybersecurity?

A 'Trojan horse' in cybersecurity refers to deceptive software that disguises itself as a legitimate application to trick users into executing it. Once activated, a Trojan can perform harmful actions such as stealing personal information, installing malware, or creating backdoors for cybercriminals to exploit the system further.

This concept derives its name from the ancient Greek story of the Trojan War, where the Greeks used a deceptive wooden horse to infiltrate the city of Troy. In a similar manner, modern Trojans lure users by masquerading as useful or harmless applications, which makes them particularly dangerous because they often bypass traditional security measures by exploiting user trust.

The other options do not align with the definition of a Trojan horse. Protective antivirus programs, tools for data recovery, and network protocols each serve different purposes in cybersecurity and have distinct functionalities that do not involve the concept of disguise or deception inherent in Trojan horses.