Trojan Horse

Trojan Horse

Trojan Horse

In computers, a Trojan horse is a program in which malicious or harmful code is contained inside apparently harmless programming or data in such a way that it can allows the unauthorized collection, falsification, or destruction of data, such as ruining the file allocation table on your hard disk. One of the most insidious types of Trojan horse is a program that claims to rid your computer of viruses but instead introduces viruses onto your computer. A Trojan horse program has a useful and desired function, or at least it has the appearance of having such. Trojans use false and fake names to trick users into dismissing the processes. These strategies are often collectively termed social engineering. In most cases the program performs other, undesired functions, but not always. The useful, or seemingly useful, functions serve as camouflage for these undesired functions. A Trojan is designed to operate with functions unknown to the victim. The kind of undesired functions are not part of the definition of a Trojan horse; they can be of any kind, but typically they have malicious intent. In practice, Trojan Horses in the wild often contain spying functions (such as a packet sniffer) or backdoor functions that allow a computer, unbeknownst to the owner, to be remotely controlled from the network, creating a "zombie computer". The Sony/BMG rootkit Trojan, distributed on millions of music CDs through 2005, did both of these things. Because Trojan horses often have these harmful behaviors, there often arises the misunderstanding that such functions define a Trojan horse. A simple example of a Trojan horse would be a program named "waterfalls.scr.exe" claiming to be a free waterfall screensaver which, when run, instead begins erasing all the files on the computer.

There are two common types of Trojan horses. One, is otherwise useful software that has been corrupted by a cracker inserting malicious code that executes while the program is used. Examples include various implementations of weather alerting programs, computer clock setting software, and peer to peer file sharing utilities. The other type is a standalone program that masquerades as something else, like a game or image file, in order to trick the user into some misdirected complicity that is needed to carry out the program's objectives.

Trojan horse programs cannot operate autonomously, in contrast to some other types of malware, like viruses or worms. Just as the Greeks needed the Trojans to bring the horse inside for their plan to work, Trojan horse programs depend on actions by the intended victims. Most antivirus programs can catch Trojan horses when scanning for viruses. Unlike viruses, however, Trojan horses don't replicate themselves. But it is possible for a Trojan horse to be attached to a virus file that spreads to multiple computers.

So as a general rule, don't open a program unless you know it is legitimate. This applies especially to e-mail attachments that are executable files. Even if you are pretty sure the attachment is OK, it is still a good idea to run it through your virus scan program (with the latest virus definitions) just to be safe. Trojan horses are almost always designed to do various harmful things, but could be harmless. Examples are

¨ Erasing or overwriting data on a computer.

¨ Encrypting files in a cryptoviral extortion attack.

¨ Corrupting files in a subtle way.

¨ Upload and download files.

¨ Allowing remote access to the victim's computer. This is called a RAT. (remote administration tool)

¨ Spreading other malware, such as viruses. In this case the Trojan horse is called a 'dropper' or 'vector'.

¨ Setting up networks of zombie computers in order to launch DDoS attacks or send spam.

¨ Spying on the user of a computer and covertly reporting data like browsing habits to other people.

¨ Make screenshots.

¨ Logging keystrokes to steal information such as passwords and credit card numbers (also known as a keylogger).

¨ Phish for bank or other account details, which can be used for criminal activities.

¨ Installing a backdoor on a computer system.

¨ Opening and closing CD-ROM tray.

 

 

References:

http://en.wikipedia.org/wiki/Trojan_horse_(computing)