Trojan horse (computing)

It's not clear where or when the concept, and this term for it, was first used, but by 1971 the first Unix manual assumed its readers knew both:[8]

Also, one may not change the owner of a file with the set—user—ID bit on, otherwise one could create Trojan Horses able to misuse other’s files.

Another early reference is in a US Air Force report in 1974 on the analysis of vulnerability in the Multics computer systems.[9]

It was made popular by Ken Thompson in his 1983 Turing Award acceptance lecture "Reflections on Trusting Trust",[10] subtitled: To what extent should one trust a statement that a program is free of Trojan horses? Perhaps it is more important to trust the people who wrote the software. He mentioned that he knew about the possible existence of trojans from a report on the security of Multics.[11][12]

Once installed, trojans may perform a range of malicious actions. Many tend to contact one or more Command and Control (C2) servers across the Internet and await instruction. Since individual trojans typically use a specific set of ports for this communication, it can be relatively simple to detect them. Moreover, other malware could potentially "take over" the trojan, using it as a proxy for malicious action.[13]

In German-speaking countries, spyware used or made by the government is sometimes called govware. Govware is typically a Trojan software used to intercept communications from the target computer. Some countries like Switzerland and Germany have a legal framework governing the use of such software.[14][15] Examples of govware trojans include the Swiss MiniPanzer and MegaPanzer[16] and the German "state trojan" nicknamed R2D2.[14] German govware works by exploiting security gaps unknown to the general public and accessing smartphone data before it becomes encrypted via other applications.[17]

Due to the popularity of botnets among hackers and the availability of advertising services that permit authors to violate their users' privacy, trojans are becoming more common. According to a survey conducted by BitDefender from January to June 2009, "trojan-type malware is on the rise, accounting for 83% of the global malware detected in the world." Trojans have a relationship with worms, as they spread with the help given by worms and travel across the internet with them.[18] BitDefender has stated that approximately 15% of computers are members of a botnet, usually recruited by a trojan infection.[19]

The term "trojan horse" in computing is derived from the legendary Trojan Horse; itself named after Troy. For this reason "Trojan" is often capitalized. However, while style guides and dictionaries differ, many suggest a lower case "trojan" for normal use.[28][29] That is the approach taken in this article - apart from when first introducing the word and its derivation.

• Computer security
• Cyber spying
• Dancing pigs
• Exploit (computer security)
• Industrial espionage
• Principle of least privilege
• Privacy-invasive software
• Remote administration
• Remote administration software
• Reverse connection
• Rogue security software
• Scammers
• Technical support scam – unsolicited phone calls from a fake "tech support" person, claiming that the computer has a virus or other problems
• Timeline of computer viruses and worms
• Zombie (computer science)

1.^ Upper case is intentional here, please see the "Orthographic note" section, and the Talk page

2.^ Lower case is intentional here, please see the "Orthographic note" section , and the Talk page

• Media related to Trojan horse (malware) at Wikimedia Commons
• "CERT Advisory CA-1999-02 Trojan Horses" (PDF). Carnegie Mellon University Software Engineering Institute. Archived from the original on October 17, 2000. Retrieved September 15, 2019.