Trojan Horse is a type of malware or malicious software. It that disguises itself as a legitimate, useful, or harmless program to trick a user into installing it. Its name comes directly from the ancient Greek myth of the wooden horse. The Greeks utilized the wooden horse to sneak into Troy. In cybersecurity, the Trojan acts as the deceptive carrier for a malicious payload.

How a Trojan Horse Works?

The core characteristic of a Trojan is its reliance on deception and user interaction, not on technical exploit alone.

• Disguise: The Trojan is packaged as something innocent, such as a free game, an email attachment (like a PDF or invoice), a seemingly necessary software update, or an installer for a legitimate program.
• Infiltration: The user is tricked into downloading and executing the file (e.g., clicking on the attachment or running the installer). Unlike a virus or worm, the Trojan cannot spread or replicate itself; it must be manually let into the system.

• Execution (The Payload): Once activated, the malicious code runs its hidden function, often in the background, without the user’s knowledge.

Common Goals (Payloads) of a Trojan

The type of damage a Trojan causes depends on the payload it carries. Some of the most common types include:

• Backdoor Trojan: Creates a backdoor a secret path on the victim’s system, giving the attacker remote, unauthorized access and control. This allows the hacker to steal data, modify files, or use the computer for other attacks (like adding it to a botnet for a DDoS attack).
• Banker Trojan: Specifically targets a user’s financial information, attempting to steal credit card numbers, online banking credentials, or e-payment system data.

• Downloader Trojan: After infecting the system, its main purpose is to download and install other types of malware (like ransomware, spyware, or keyloggers) onto the device.
• Ransom Trojan: A form of ransomware that locks or encrypts files and demands a ransom payment to restore access.

In summary, a Trojan Horse is one of the most dangerous types of malware because it uses social engineering to bypass initial defenses by tricking the most unpredictable element: the user.