Understanding Trojan

The term Trojan Horse (Trojan Horse) comes from Greek mythology during the Trojan war. Greek forces in the battle against the Trojan royal army. Greek troops had surrounded the city of Troy for ten years, but because of the Trojan royal army strong enough, it is difficult to defeat the Greek army. Finally, the Greek army to make a strategy that is by making a giant horse made of wood. Wooden Horse is quite unique, hollow inside so it can fill the Greek army. The Greek army pretended to withdraw and handing him the prize was a giant wooden horse. With the help of a Greek spy named Sinon, residents of the city of Troy was convinced to accept the giant wooden horse, and put it into the city. In the evening, the Greek soldiers inside the wooden horse came out, then opened the gate and attacked the city of Troy. In this way the city of Troy can be controlled by Greece. Epic story above has been inspired hackers to create the "intruders" into someone else's computer called Trojan Horse. Trojan currently associated with computer security issues seriously enough. Trojans can log into the computer with a number of ways and from different sources is less reliable on the Internet or from others [1]. Like a virus, trojan amount which progressively increased in number, because of hackers or Trojan program creator (programmer) who is always experimenting with ways to develop it. Trojans do not have the active period, meaning the Trojans will be there forever (nested) and never will be exhausted. There are many things that can be developed by programmers that created the program is undetectable by anti-virus or trojan scanner. Programmer will always experimenting to create a unique Trojan with new functions with a more powerful encryption method. Technically, a Trojan can appear anywhere and anytime, on any operating system and various platforms. Circulation speed as fast as Trojan viruses. In general, Trojans come from programs downloaded from the Internet, especially freeware or shareware suspicious and not from the original site. One indication of computers infected by the Trojan can be described as follows. At the time the computer is connected to the Internet, for example, when chatting (chating) or checking e-mail, but hard drive work with busy (busy) in a long time. In addition users also are not running a large application program or download something that requires a long spinning disk hard drives. The incident including the strange events suspicious of infiltration.

 Definition Trojan
Trojan on the computer system is a program that is not expected and is inserted without the knowledge of computer owners. The program can then be activated and controlled remotely, or by using a timer (timer). As a result, the inserted Trojan Horse computer can be controlled remotely. Another definition says that the trojan is any program that is used to perform an important function and are expected by the user, but the code and functions in it are not known by the user. Furthermore, programs implementing the unknown function and is controlled remotely from the unwanted by users.
Trojan Function
Trojan lurking in the background by opening certain ports and waiting is activated by the attacker. Infected computers can be controlled by the attacker through his version of the client [10]. How it works similar to the Trojans and remote administration tool, with the same properties and functions. Remote administration programs such as pcAnywhere, is used for the purposes of the true and legitimate (legitimate), while Trojam used for negative purposes.
When a computer is infected by Trojan and has been controlled by the attacker, then several possibilities can occur. For example, a Trojan by the name of NetBus can do many things to computers that have been controlled, among others:
• delete a file, 
• send and retrieve files, 
• running the application programs,  
• display images, 
• peer programs that are running, 
• close the programs you run,  
• see what is being typed, 
• open and close the CD-ROM drive,  
• send messages and invite to talk (chat),  
• Turn off the computer.
The above example is only part that can be done by a Trojan. Another possibility Trojans have different functions maybe even more dangerous and more difficult to detect. In an application online shopping, the Trojan is one threat to the sellers and buyers. Trojans can be used to steal credit card numbers by capturing keystrokes when doing online transaction processing. Another way is to exploit the security hole in the side on the operating system vendor or service provider (server) is used to tap customer data (the client). If the hole is exploited, the possibility of all customer data from the server to crash into the hands of bugs.