"Malware that looks like something beneficial but has a malicious component. Users are tricked into downloading and installing the malware, thinking it’s worthwhile. After the user installs the Trojan, the malicious component runs. Trojans are named after the Trojan horse from Greek mythology." (Darril Gibson, "Effective Help Desk Specialist Skills", 2014)
"A program posing as a harmless piece of software that can contain malware such as viruses or spyware." (Andy Walker, "Absolute Beginner’s Guide To: Security, Spam, Spyware & Viruses", 2005)
"Malicious code that creates backdoors, giving an attacker illegal access to a network or account through a network port." (Linda Volonino & Efraim Turban, "Information Technology for Management 8th Ed", 2011)
"software that appears to be an application but is, in fact, a destructive program." (Bill Holtsnider & Brian D Jaffe, "IT Manager's Handbook" 3rd Ed., 2012)
"An apparently useful and innocent program containing additional hidden code that allows the unauthorized collection, exploitation, falsification, or destruction of data. A Trojan is often received from a familiar e-mail address or URL or in the form of a familiar attachment." (Mark Rhodes-Ousley, "Information Security: The Complete Reference" 2nd Ed., 2013)
"A form of malware application hidden within another application that introduces backdoor access." (Mike Harwood, "Internet Security: How to Defend Against Attackers on the Web 2nd Ed.", 2015)
"A malicious program disguised as a benevolent resource" (Nell Dale & John Lewis, "Computer Science Illuminated, 6th Ed.", 2015)
"A piece of malicious software that looks harmless but has a detrimental effect on a computer when it runs." (Faithe Wempen, "Computing Fundamentals: Introduction to Computers", 2015)
"A program that is disguised as another program with the goal of carrying out malicious activities in the background without the user knowing." (Adam Gordon, "Official (ISC)2 Guide to the CISSP CBK" 4th Ed., 2015)
"A piece of software or code that is disguised as a legitimate software that is created with the intention to breach a system or networks security." (Hamid R Arabnia et al, "Application of Big Data for National Security", 2015)
"Software that either hides or masquerades as a useful or benign program." (Weiss, "Auditing IT Infrastructures for Compliance" 2nd Ed., 2015)
"A computer program that appears to have a useful function, but also has a hidden and potentially malicious function that evades security mechanisms, sometimes by exploiting legitimate authorizations of a system entity that invokes the program." (O Sami Saydjari, "Engineering Trustworthy Systems: Get Cybersecurity Design Right the First Time", 2018)
