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Computer Security - How Do Trojan Horses Work?

written by: •edited by: Lamar Stonecypher•updated: 5/16/2010

Hackers accessing your PC via the "backdoor" is a very real threat, especially with "Trojan Horse" tools available for malicious purposes. This article explains how a Trojan Horse works as well as steps you can take to prevent their use on your system.

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    What is a Trojan Horse?

    Trojan horses are malicious PC tools or applications that appear innocent (and at times pleasing), but which in fact are equipped with software that can be potentially devastating.

    Like the Greek myth of the Trojan horse, software “Trojans" can be used to steal data or even act as keylogging software.

    The use of these Trojans is illegal and dangerous. Discovery of such a tool on your system should prompt you into immediate action – a removal tool such as Spybot Search & Destroy would be a good option for anyone intending on using their machine securely.

    But how does a Trojan horse work, exactly?

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    How Does a Trojan Horse Work?

    In Greek mythology, the story of the Trojan Horse is a tale from the Trojan War in which the Greeks waged war with the city of Troy. After a fruitless ten-year campaign, the attackers decide to build a huge wooden horse as a gift for the Trojans. Fooled into accepting the gift, and seeing no sign of the Greek army, the Trojans wheel the horse into Troy – only for a platoon of Greek soldiers to emerge from within later than night and open the gates to the city, letting in the rest of the army.

    Computer Security - How Does A Trojan Horse Work? The analogy with software Trojans is clear – it represents a backdoor into your PC via a method that appears trustworthy, but in actual fact is usually destructive if not quickly countered.

    Trojans can be acquired in the following ways:

    • Email attachments.

    • Application exploits, such as vulnerabilities in web browsers or messaging clients – regular Windows Updates should prevent exposure to this method. See Solving Windows Security Problems by Checking for Updates for more on this.

    • A common method with the arrival of highspeed internet is via websites containing executable content, such as ActiveX. A competent Internet security suite should provide protection in conjunction with an up to date browser.

    • Finally, software downloads from either hosting sites or filesharing networks can be laced with a variety of malware, including Trojans.

    Each of these methods can include one or more overwhelming intrusions upon your computer security.

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    Consequences of a Trojan

    The consequences of a Trojan on your PC are potentially life-changing. These results can include data theft such as passwords or other sensitive information you might have on your PC, keystroke logging, remote viewing and control of your PC, and even downloading and uploading of files to and from your computer. Further uses of a Trojan include hijacking your PC to use it as part of a botnet (a network of drone PCs used to perform spamming), installing more malware or even just really annoying you by crashing your computer.

    However you receive a Trojan, you will need to resolve any infection almost immediately.

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