What is a Trojan horse ? - Security Term

A Trojan horse, or trojan for short, is a term used to describe malware that appears, to the user, to perform a desirable function but, in fact, facilitates unauthorized access to the user's computer system. The term comes from the Trojan Horse story in Greek mythology. the Trojan horse was given to the Trojans by the Greeks during a siege as gift of surrender. The Trojans, happy with victory against the Greeks accepted the enormous horse as a gift without realizing that it was filled with Greek soldiers. While the Trojans partied the Greeks came out of the horse and opened the gates to allow their entire army to enter inside the walls of Troy. Trojan malware works much the same way, it pretends to be something it is not and fools you into accepting it into your computer, where it will run and do whatever it is intended to do, sometimes without your knowledge.

Trojan horses are not self-replicating which distinguishes them from viruses and worms. Additionally, they require interaction with a hacker to fulfil their purpose. The hacker need not be the individual responsible for distributing the Trojan horse. It is possible for hackers to scan computers on a network using a port scanner in the hope of finding one with a Trojan horse installe rojan horses are designed to allow a hacker remote access to a target computer system. Once a Trojan horse has been installed on a target computer system it is possible for a hacker to access it remotely and perform operations. The type of operations that a hacker can perform are limited by user priviliges on the target computer system and the design of the Trojan horse itself.

Operations which could be performed by a hacker on a target computer system include deletion of files, modification of files, uploading and downloading of files, installation of software (including other malware), and data theft.

There are many Antivirus softwares that are designed to detect and delete Trojan horses ideally preventing them from ever being installed. It may be possible to remove a Trojan horse manually given a full understanding of how that particular Trojan horse operates, however if it is possible that a Trojan horse has been used by a hacker to access a computer system it will be difficult to know what damage has been done and what other problems have been introduced. In situations where the security of the computer system is critical it is advisable to rebuild it from known good software.


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