What is a Trojan Virus?

A trojan virus is a software program that masks itself as something it’s not. Usually trojans pose as an innocent download or email attachment but it can take on any disguise in its attempts to get onto a computer. Trojans need human interaction to spread from one computer to the next. This means you need to download something or open an email attachment for the trojan to access your computer. Once executed, it can corrupt files, steal user information like passwords and answers to security questions, and add more trojans and other malware to your PC. There are trojan programs designed to kill antivirus measures and remote access trojans that steal information from your browser history and send it automatically to the program creator to be used and abused for their own unethical purposes.

A Brief History of Trojans

The first trojan, called ANIMAL, was developed for the UNIVAC 1108 in 1975 by John Walker and was intended to be non-malicious. He thought of his little program as a game of sorts and meant no harm by it. Then came Spy Sheriff which was one of the earliest trojans to go, erm, viral, as affected millions of users in its wake by inundating them with pop-ups. The pop-ups led the unfortunate clicker to malware-laced websites. Vundo appeared in 2004 and had a similar method of directing users to malware laden sites, but it also deployed denial of service (DoS) attacks on Google and Facebook. Later Zeus was discovered. This incarnation captures information from banking websites and can therefore access your money – clearly very malicious. Each trojan’s goal is project-specific, but you can be sure that now, ten times out of ten, the objective of any trojan is less than genial and that it’s out to harm your system in one way or another.

How Did I Get a Trojan on My Computer?

Developers may send mass emails with the attachment harboring malware or take the email addresses out of the infected users address book. Trojans can also be sent via Skype or text message and can even be embedded in video players in Twitter and Facebook. Their goal is usually to gain access to PCs to get credit card information or other sensitive material or corrupt data. Any email attachment, game download, or ebook needs to be thought of as a potential threat to your computer’s security. Once the attachment is opened or the link is clicked, the trojan will start up each time you start your PC or Mac  (Yes, all you Mac fanboys, they are susceptible to trojans as well.) The malicious program can even turn your PC into a zombie computer as part of a botnet (more on botnets later, stay tuned), or a network of infected computers that try to infect other computers.

How Can I Keep My Computer Safe from Trojans in the Future?

Trojans tend to work quietly in the background and can sit dormant for years without being noticed. If your antivirus malware blocker isn’t up to date and you aren’t running regularly scheduled scans, you may never find out about the damage that’s being perpetrated right there, inside your computer. Make sure you are running an up to date antivirus and malware blocking program like RCS that has the ability to schedule scans so your computer is being checked regularly. And use your head – stay away from email attachments and shady downloads.

Sources:
http://computer.howstuffworks.com/trojan-horse1.htm
http://www.tech-faq.com/trojan-virus.html
http://en.wikipedia.org/wiki/Timeline_of_computer_viruses_and_worms

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