What is trojan horse?

Trojan horse

Trojan horse or Trojan is a malicious computer program that is often disguised as legitimate software. It is a program that appears harmless, but used to hack into a computer by misleading users of its true intent. Name Trojan horse, derived from the Ancient Greek story of the wooden horse.

Attackers have long used Trojan horses as a way to trick end users into installing malware.  Trojans can be employed by cyber-thieves and hackers trying to gain access to users' systems. Users are typically tricked by some form of social engineering into loading and executing Trojans on their systems.

Typically, the malicious programming is hidden within an innocent-looking email attachment or free program, such as a game. When the user downloads the Trojan horse, the malware that is hidden inside is also downloaded. Once inside the computing device, the malicious code can execute whatever task the attacker designed it to carry out. This infection allows an attacker to access users' personal information such as banking information, passwords, or personal identity.

How Trojans can impact you

Unlike computer viruses and worms, Trojans generally do not attempt to inject themselves into other files or self-replicate. Because the user is often unaware that he has installed a Trojan horse, the computing device's security depends upon its antimalware software recognizing the malicious code, isolating it and removing it. Trojans are classified according to the type of actions that they can perform on your computer:

1. Rootkit - Rootkits are designed to conceal certain objects or activities in your system.  Often their main purpose is to prevent malicious programs being detected.

2. Exploit - Exploits are programs that contain data or code that takes advantage of a vulnerability within application software that’s running on your computer. 

3. Backdoor - Trojan gives malicious users remote control over the infected computer.  They enable the author to do anything they wish on the infected computer – including sending, receiving, launching, and deleting files, displaying data, and rebooting the computer.

4. DDoS -  DoS attacks against a targeted web address  by sending multiple requests from your computer and several other infected computers.

5. Spy - Trojan-Spy programs can spy on how you’re using your computer. For example, by tracking the data you enter via your keyboard, taking screen shots, or getting a list of running applications.

How to protect yourself against Trojans

To avoid being infected by Trojan malware, users should keep their antivirus software up to date, never download files or programs from untrusted sources, and always scan new files with antivirus software before opening them.