Trojan Horse

There are 2 programs :

• server program that's installed on victim's computer (usually without the victim having knowledge of its effect)
• client program on non-victim's computer
  

The concept is quite simple :

• non-victim connects to victim's computer
• non-victim sends whatever he/she wants
  

There are 2 simple things about connecting to others, which is :

• ip address : local computer has 127.0.0.1 automatically, there are another conventions like IPv6 if you interested
  
• ports : there are only 65535 ports so try not using 'any higher number or any already used port, this port requirement make us possible to become victim and non-victim at the same computer.

There are various tools to make trojan horse program, which needs programming skill to build it. I believe there are tutorial everywhere for sharpening your programming skill.

The program needs to be installed, no matter what triggered the installation. These are the list of possibility on how to install trojan horse to victim's computer :

• p2p : like kazaa, winmx
• email attachments
• websites

The reason to install trojan horse is either information retrieval or controlling other computers. Trojan horse that retrieve information is much more easier to make. Controlling other computers needed quite a knowledge about how operating system works on victim's computer. Well, that's only if you want to make it on your own.