text: how trojan horse work ? explain in detail. if possible then must be with diagram or step ..?   hi!  a trojan horse is a program (application) that has vile code contained in it. once it gets in your computer (and there are many ways) it runs (it can be set to run). it configures your system to load and run it every time your computer starts. it waits, patiently, for a client application (known as trojan client) to connect (most of the time by username and pass), then takes control of the system. once the client is connected the user of the trojan has much control of the system, to most files and folders, application... the confidential data on it becomes quite public, that's why, a trojan (horse) is the no 1 security threat. literally, the trojan makes the system... insecure, and so, one can get all your passwords, accounts, personal data, leading, in many cases, to identity theft. nasty!  good luck!