First of all it would be useful to state that a Trojan horse virus represents an infectious program able to cause serious damage to a computer. The Trojan horse can infect a user's machine without being noticed. As soon as it penetrates a computer, the Trojan horse scans it with the goal of stealing personal data.
One of the earliest Trojan horse viruses was detected in the 1980s, when several computers were affected. As it was earlier mentioned Trojan horse viruses are created in order to steal useful information such as passwords. They are developed by hackers, who, after stealing data, can use the information for various purposes, including blackmailing. Some of the first Trojan horse viruses were able to infect Windows32 files, but since then these programs evolved, and today they can cause even more harm.
The name of the Trojan horse comes from a story from Greek mythology about the siege of Troy. Greeks were unable to conquer the city until they built a huge wooden Trojan horse and hid a number of warriors in it. The wooden horse was supposed to be a present from the Greeks, informing that they sailed away and no longer wanted to conquer the city. When the Trojan horse was pulled into the city, the small army of Greeks inside it waited till dark and then invaded the Troy, destroying it, thus leading to the end of the war. In contrast to the wooden Trojan horse, the Trojan horse virus spread worldwide and is still popular today.
According to some online sources the first Trojan horse virus was dubbed the pest trap, also known as Spy Sheriff. This Trojan horse managed to infect about one million PCs worldwide. It did not damage any files on a computer, instead it led to the appearance of a large number of pop-ups, most of them looking like warnings that warned users about the necessity to installs some kind of software application. As soon as the Trojan horse computer virus was installed on the machine, it was quite difficult to get rid of it. In case the user tried to erase it, the Trojan horse would simply reinstall itself from hidden affected data files on the computer.
Often Trojan horse viruses come in packages that at first sight seem to be rather harmless. However, this is exactly what a Trojan horse should do until it affects a computer so hackers could remotely control the programs of the infected machine. There was a popular case that involved a professor who was accused of downloading about 1,000 child porn images, but who was released after it was discovered that the professor's computer was affected by a Trojan horse virus that downloaded the pictures. Despite the false accusations, the outcome of the situation had a serious impact on the professor's reputation.
During the 1980s there was an increase of the Bulletin Board System, which was computer system running software that permitted users to penetrate the system through a phone line. The BBS contributed to a fast spread of Trojan horse viruses, because after users logged in, they carried out such functions as uploading and downloading software and data sharing (some of which was infected). At that time computer viruses were created to aim popular software traders.
A dangerous Trojan horse virus was the Vundo, which used a lot of memory of the operating system at different intervals and generated a lot of pop-ups that informed the user about a number of software programs that need to be installed on the computer. The installed software included one or more computer viruses. Unlike the Spy Sheriff, it was rather easy to get rid of Vundo. There is one important thing to remember: a Trojan horse virus cannot be turned on unless a user doesn't activate the program that features the virus. It is important that you do not download unknown programs, especially if someone or something persuades you to do so. link....