This document provides an overview of Trojans and backdoors. It defines a Trojan as a program that contains malicious or harmful code inside apparently harmless programming or data, allowing it to gain control and cause damage. The document discusses how hackers use Trojans and backdoors to steal sensitive information from personal devices and online banking accounts. It outlines the objectives of the CEH lab, which are to help students learn how to detect and defend against Trojan and backdoor attacks by creating sample Trojans, detecting vulnerabilities, and documenting results.