Trojan horse (computing)

A Trojan horse, or Trojan, is a type of malware that masquerades as a legitimate file or helpful program but whose real purpose is eg to grant a hacker unauthorized access to a computer. Trojans do not attempt to inject themselves into other files like a computer virus. Trojan horses may steal information, or harm their host computer systems.^[1] Trojans may use drive-by downloads or install via online games or internet-driven applications in order to reach target computers. The term is derived from the Trojan Horse story in Greek mythology because Trojan horses employ a form of “social engineering,” presenting themselves as harmless, useful gifts, in order to persuade victims to install them on their computers.^{[2][3][4][5][6]}

Purpose and uses

A Trojan may give a hacker remote access to a targeted computer system. Operations that could be performed by a hacker on a targeted computer system may include:

• Use of the machine as part of a botnet (e.g. to perform automated spamming or to distribute Denial-of-service attacks)
• Electronic money theft^[7]
• Data theft (e.g. retrieving passwords or credit card information)
• Installation of software, including third-party malware
• Downloading or uploading of files on the user's computer
• Modification or deletion of files
• Keystroke logging
• Watching the user's screen
• Crashing the computer
• Anonymizing internet viewing

Trojan horses in this way may require interaction with a hacker to fulfill their purpose, though the hacker does not have to be the individual responsible for distributing the Trojan horse. It is possible for individual hackers to scan computers on a network using a port scanner in the hope of finding one with a malicious Trojan horse installed, which the hacker can then use to control the target computer.^[8]

A recent innovation in Trojan horse code takes advantage of a security flaw in older versions of Internet Explorer and Google Chrome to use the host computer as an anonymizer proxy to effectively hide internet usage. A hacker is able to view internet sites while the tracking cookies, internet history, and any IP logging are maintained on the host computer. The host's computer may or may not show the internet history of the sites viewed using the computer as a proxy. The first generation of anonymizer Trojan horses tended to leave their tracks in the page view histories of the host computer. Newer generations of the Trojan horse tend to "cover" their tracks more efficiently. Several versions of Slavebothave been widely circulated in the US and Europe and are the most widely distributed examples of this type of Trojan horse.^[8]