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What is the Trojan Horse Virus?

In computing, a Trojan horse, or Trojan, is a type of malware/malicious computer program or piece of code that appears to be a legitimate program but can take control of your computer or mobile devices.

Trojans are designed to steal sensitive information, cause damage to your computer or the files in your computer, or inflict some other harmful action on your data or network.

Named after the “Trojan Horse” from the Greek epic poem “The Iliad,"  a Trojan malware works precisely as the wooden horse stated in the poem.

The Greeks constructed a giant wooden horse to trick their enemies, the Trojans received the horse into the city as a gift. But the horse carried a legion of soldiers who brought ruin to the city of Troy from the inside later that night.

Trojan malware works exactly like that, acting like a normal application or file to trick users. And when the unsuspecting user loads or executes the malware on their device, the Trojan delivers the payload, bringing ruin to the device/network.

Trojans are sometimes called Trojan Virus or Trojan Horse Virus, however, since Trojans can’t execute and replicate by themselves, the user has to execute a Trojan to activate it. That’s why Trojans don’t fall under the computer virus category but rather the general malware category. 

Virus or not, Trojans are certainly disruptive and an inconvenience at the very least. So it’s smart to know how they work and how to keep your devices safe.


How do Trojans Work?

As we’ve mentioned, Trojans disguise themselves as legitimate files or software to trick people into loading/executing them on their devices. Once executed, they infect the device, cause damage to the files on the computer, or disrupt/transfer data to cybercriminals.

Trojans can spread in many ways, including through random email attachments, malicious websites, or unofficial applications/software. Cybercriminals trick users with attractive offer pop-ups in their windows or send attractive ad campaigns through email as well.

When a user clicks on these links, they might get redirected to malicious websites, or directly download Trojans onto their devices. These Trojans then damage, disrupt, or transfer the user’s data to cybercriminals and compromise the system or network.

Trojan attacks affect laptops, desktops, smartphones, tablets, and other smart devices.

It is almost impossible to put these apps on legitimate app markets. But they can be found on unofficial app markets and random websites. Certain Trojans are specifically designed to attack only Android devices and pass information without the user’s consent.

A Trojan Horse compromises a mobile’s security, leading the hackers to take control of the home/office routers. Once cybercriminals take control of the data traffic, they can redirect the traffic and take part in criminal activities anonymously.

Types of Trojan Malware

There is a wide variety of Trojan malware available on the internet. Let’s take a look at the 15 most dangerous Trojan malwares and how they operate:


  1. Backdoor Trojans: A backdoor Trojan creates a secret communication tunnel—a backdoor, if you will, that allows the attacker to remotely access the infected system from anywhere. This lets the hacker control the device, monitor or steal data, and deploy other software. This kind of Trojan operates in the background and is very hard to detect.
  2. Rootkit Trojan: Rootkit Trojans can gain root-level or administrative access to a machine, and boot with the operating system. Rootkits give attackers full control over a system or a framework without informing the user, which makes them very difficult to detect or remove. Bootkits, firmware rootkits, and kernel-level rootkits are some examples of rootkit Trojans.
  3. Download Trojan: A Downloader Trojans work by downloading and executing unwanted, malicious programs or applications, including other types of Trojans and adware. Downloader Trojans are a part of a multi-stage Trojan attack, followed by the installation of other types of Trojans that give cybercriminals a consistent foothold on the system.
  4. Banking Trojan: Banking Trojans are crafted to exploit the financial login credentials of a user. Generally, banking Trojans exploit banking systems and payment methods like credit cards and transfer the extracted confidential information to the attacker behind the Trojan’s deployment.
  5. Ransomware Trojans: Ransomware Trojans are spread by malicious email attachments or software. After installing or opening the file or application, a ransomware Trojan blocks the user from accessing their system or specific data like documents, pictures, or all the folders in the system.
    The user can gain access to their corrupted resources only by fulfilling the demand of the attacker, usually by paying the ransom. CryptoLocker, Petya, Locky, WannaCry, Cerber, etc. are some of the most renowned ransomware Trojans.
  6. Spy Trojan: Spy Trojan refers to applications of programs cybercriminals use to spy on someone virtually. Spy Trojans monitor the activities on a device, record keystrokes of a user by using a keylogger, and steal valuable sensitive information like passwords, pins, financial account information, etc.
  7. Distributed Denial-of-Service (DDoS) Attack Trojan: A distributed denial-of-service (DDoS) attack works by repeatedly sending requests to the target system or network to a point where it becomes unable to process regular traffic, causing the system/network to shut down.
  8. Exploit Trojans: Exploit Trojans contain malicious code or scripts that are programmed to attack vulnerable applications or software in a system. It usually happens when the software has a secure hold during development.
  9. Mailfinder Trojan: Mailfinder Trojans are exactly what it sounds like: they extract email addresses from the infected machine or network, and transfer the emails to the attacker via email, web, FTP, or other methods.
  10. Fake AV (Anti-Virus) Trojan: Fake antivirus Trojans behave like antivirus software and demand money in exchange for protecting the affected system. Mostly, these fake AVs misrepresent the security status of the infected computer and show that the system is compromised, and the only way to get out of the situation is to purchase some form of paid service.
    If the victim pays out, the fake AV brings up new issues and asks for more money, putting the victim in a never-ending blackmailing cycle.
  11. Remote Access Trojan (RAT): A Remote Access Trojan connects the infected device to a remote device, giving the attacker full control over the device to perform various malicious activities.
  12. Infostealer Trojans: Infostealer Trojans gain illegal access to the victim’s confidential data, such as login credentials, financial information, etc. After that, the attacker sells this data to the black market.
  13. Dropper Trojan: Dropper Trojans are a type of downloader Trojan that installs on a computer and deploys other malware components. For example, a dropper Trojan can be utilized to inject a backdoor into a sensitive server.
  14. GameThief Trojan: GameThief Trojan's primary targets are gamers. This type of Trojan is programmed to steal user data from a gamer’s account.

Some other noteworthy examples of Trojan malware include:

  • Clicker Trojan
  • Notifier Trojan
  • Proxy Trojan

How to Prevent a Trojan Horse Malware Attack?

Just like every other cybersecurity concern, prevention is always better than cure. Here are a few precautions you can take to be safe from Trojan attacks: