What Is a Trojan Horse? Is It a Virus or Malware?

Updated on September 26, 2024.

A Trojan horse, or Trojan, is a type of malware that disguises itself as legitimate software or files to infiltrate a system. Trojan horses often get mistaken for viruses, but they are not viruses – they are a type of malware. Oftentimes, you may see people refer to Trojans as “Trojan viruses” or “Trojan horse virus,” but these names are misleading. While both Trojans and viruses are a type of malware, this does not make Trojans viruses since they differ in how they spread and infect devices.

Continue reading to learn more about Trojan horse malware and how to protect your devices from infection.

How Trojan horse malware works

Trojan horse malware works by hiding inside files that look innocent, deceiving users who download or click on them. Since Trojans can’t replicate by themselves like viruses, they rely on a potential victim downloading it on their system for it to work. Once a computer is infected by Trojan malware it can also spread to other computers by the cybercriminal turning the infected device into a zombie computer. A zombie computer is when a cybercriminal has remote control over a device without the victim knowing. 

Cybercriminals can then use the zombie computer to continue sharing malware across different devices to people in the victim’s contacts.

How Trojan horse malware infects devices

Trojan horse malware can infect devices by the victim downloading malicious email attachments, fake software, or by clicking on malicious links.

Downloading malicious email attachments

Downloading malicious email attachments is one of the primary ways a Trojan horse can infect a device. This often begins with a well-crafted phishing email. Cybercriminals may impersonate organizations or individuals you trust, making the content and appearance of the phishing email almost indistinguishable from a legitimate email. These phishing emails often contain malicious attachments that appear safe but are designed to infect your device with malware. If you open these attachments, Trojan can enter the computer without detection and get installed. 

Downloading fake software

Another way a Trojan horse can infect your device is if you download fake software from the internet. Cybercriminals often create software programs that mimic legitimate software and offer them for free or at a heavily discounted rate, enticing victims to download it. These programs are so skillfully crafted that it’s hard to tell they’re illegitimate, leading victims to download and install them without verifying the source or developer.

Clicking on malicious links

Trojan horses can also infect devices by you clicking on malicious links. Cybercriminals create malicious links and then lure victims into clicking them by placing them in places where potential victims won’t suspect anything such as in emails, social media, online advertisements and even spoofed websites. Clicking on a malicious link can immediately begin downloading Trojan horse malware onto your device. 

How to prevent Trojan horse malware infection

To prevent infection by a Trojan horse and other types of malware, it’s important to follow basic cybersecurity best practices such as the following: 

Avoid opening unsolicited email attachments

One measure to prevent infection by a Trojan horse is to avoid opening unsolicited email attachments. Before deciding to open an email attachment, check if the sender is trustworthy. Emails from unknown senders or unfamiliar addresses require extra caution. Even if the email seems to come from friends, colleagues or other trusted senders, be wary if the attachment is unexpected or doesn’t fit the context of the email.

Don’t click unsolicited links

To avoid infection by a Trojan horse, it’s very important not to click links on suspicious-looking websites or links that are sent to you unsolicitedly through text, email or messaging apps because they could potentially infect your device with malware. Rather than clicking on a link immediately after someone sends it to you, check if it’s safe by safely copying the link and pasting it into Google Transparency Report. 

Only download apps and software from official sources

Another important measure to avoid infection by a Trojan horse is to refrain from downloading software from sources other than official stores. Software downloaded from places other than official app stores or the developer’s website may carry the risk of containing Trojans or other malware. 

Stick to downloading from official sources like Apple’s App Store or the Google Play Store. 

Invest in antivirus software

Antivirus software is a program you can install on your computer that can detect and remove malware before it’s able to infect your device. Some antivirus software programs also come with the capability to scan email attachments for malware. If malware is detected in an email, the antivirus software removes it from your inbox to prevent you from clicking it. 

Keep your device’s Operating System (OS) up to date

As a measure to prevent infection by a Trojan horse and other malware, keep your device’s operating system and applications up-to-date. These updates contain important security patches that fix known vulnerabilities. Software updates also provide your devices and applications with new security features and fix bugs to make your devices and applications run smoother. 

Stay protected against Trojan horse malware

Taking measures to prevent Trojan horse and other malware infections can help keep your personal information safe from getting into the hands of cybercriminals. Following basic cybersecurity measures such as being cautious of what you click, download, and keeping your devices up to date can make all the difference in keeping yourself protected.