What is a Trojan Horse? Definition, Examples and More (original) (raw)

Last Updated : 23 Jul, 2025

The name "**Trojan Horse" is taken from a classical story of the Trojan War. It is a code that is malicious and has the capacity to take control of the computer. It is designed to steal, damage, or do some harmful actions on the computer. It tries to deceive the user to load and execute the files on the device. After it executes, this allows attackers to perform actions on the user's computer like deleting data from files, modifying data from files, and more. Now like many viruses or worms, Trojan Horse does not have the ability to replicate itself.

Trojans account for **58% of all computer malware. Every minute, four companies fall victim to ransomware attacks

**Features of a Trojan Horse

• **Steals Information: Trojan horses are often designed to steal sensitive information such as passwords, banking details, and other personal data stored on the victim's computer.
• **Remote Access: A Trojan horse can grant remote access to an attacker, allowing them to control the infected system and perform actions without the user's knowledge or consent.
• **Data Deletion: Some Trojan horses are capable of deleting or corrupting data on the user's computer, causing data loss or system instability.

How Does Trojan Horse Work?

Unlike computer viruses, a **Trojan Horse requires a user to download and install the malicious software for it to function. It cannot manifest or execute by itself. For a Trojan to target a device's system, the user must download and run the executable file (.exe).

**Methods of Propagation

1. **Email Attachments:
   Spammers often send emails with attachments that appear to be legitimate but actually contain Trojan malware. When the user opens the email and downloads the attachment, the Trojan installs itself and runs automatically every time the infected device is turned on or the email is accessed.
2. **Social Engineering:
   Cybercriminals use **social engineering techniques to trick individuals into installing malicious software. They may disguise Trojans in internet links, pop-up ads, or banner advertisements. These deceptive methods increase the likelihood of the user clicking on malicious content.
3. **Infection Through Infected Devices:
   Once a device is infected, it can propagate the Trojan to other computers. The hacker can turn the infected device into a **zombie computer, allowing remote access without the user's knowledge. These compromised devices are often used to spread malware to other systems, forming a **botnet.

**User Interaction and Impact

A Trojan can remain dormant without noticeable symptoms until the user interacts with specific applications or websites. For example, a user may receive an email from a friend with an attachment that appears harmless. Once downloaded, the attachment runs malicious code that installs the Trojan without the user's awareness, and the machine continues to function normally, masking the infection.

**Activation and Consequences

The Trojan remains undetected until the user engages in certain activities, such as visiting a specific website or logging into a banking app. Upon this interaction, the Trojan becomes activated, and the malware executes its intended malicious action, such as stealing data, causing system damage, or gaining unauthorized access. Depending on the type of Trojan and its programming, it may destroy itself, go dormant, or continue running malicious processes on the device.

Types of Trojan Horse

Trojans are designed to enter a system without being detected and execute malicious actions, they can be classified on the basis of specific targets and action as follows

• **Backdoor trojan: gives the attacker remote access to the compromised machine.
• **Ransom trojan: encrypt the data on the compromised system and then demand payment in exchange for its decryption.
• **Trojan Banker: steal the account data for online banking, credit and debit cards, etc.
• **Trojan Downloader: download many malicious files like the new versions of Trojan and Adware into the computer of the victims.
• **Trojan Dropper: prevent the detection of malicious files in the system. It can be used by hackers for installing Trojans or viruses on the victim's computers.
• **Trojan GameThief: steal data from Online Gamers.
• **Trojan I's: steal login credentials and passwords

Other Trojans can also be used like: -Trojan-notifier, Trojan-clicker, and more.

Examples of Trojan Horse Attacks

Trojan has been used several times to attack systems, a few notable examples include:

• **Rakhni Trojan: The Rakhni Trojan infects devices by delivering ransomware or a cryptojacker utility that allows an attacker to utilize a device to mine bitcoin.
• **Tiny Banker: With the use of Tiny Banker, hackers can steal users' bank information. As soon as it infected, it was discovered at least 20 U.S. banks.
• **Zeus or Zbot: Zeus, often known as Zbot, is a toolkit that allows hackers to create their own Trojan virus and targets financial services. To steal user passwords and financial information, the source code employs strategies like form grabbing and keystroke logging.

**Prevention from Trojan Horse Attacks

To protect against Trojan Horse infections, it's essential to follow preventive measures to minimize the risk. Here are the basic steps you can take to safeguard your system:

**1. Avoid Downloading from Unsecured Websites

Refrain from downloading images, audio files, or any other content from untrusted or unsecured websites. These files may carry malicious code that can install Trojans on your device.

Do not click on pop-up advertisements, especially those promoting online games or other suspicious offers. These ads can often redirect you to malicious sites or prompt downloads of infected files.

**3. Do Not Open Unknown Attachments

Avoid opening email attachments from unfamiliar or unknown sources. Attachments from unsolicited emails may contain Trojans or other malware designed to infect your system once opened.

**4. Install and Update Antivirus Software

Ensure that you have reliable antivirus software installed on your device. Regularly update the software to ensure it can detect and remove the latest Trojan threats. A good antivirus program will scan and identify potentially harmful files before they can damage your system.