What is a Trojan?*


A Trojan Horse, or Trojan, is a type of malicious code or software that looks legitimate but can take control of your computer. A Trojan is designed to damage, disrupt, steal, or in general inflict some other harmful action on your data or network. A Trojan acts like a bona fide application or file to trick you. It seeks to deceive you into loading and executing the malware on your device. Once installed, a Trojan can perform the action it was designed for. A Trojan is sometimes called a Trojan virus or a Trojan horse virus, but that’s a misnomer. Viruses can execute and replicate themselves. A Trojan cannot. A user has to execute Trojans. Even so, Trojan malware and Trojan virus are often used interchangeably. Whether you prefer calling it Trojan malware or a Trojan virus, it’s smart to know how this infiltrator works and what you can do to keep your devices safe.


How do Trojans work?


Here’s a Trojan malware example to show how it works. You might think you’ve received an email from someone you know and click on what looks like a legitimate attachment. But you’ve been fooled. The email is from a cybercriminal, and the file you clicked on — and downloaded and opened — has gone on to install malware on your device. When you execute the program, the malware can spread to other files and damage your computer. How? It varies. Trojans are designed to do different things. But you’ll probably wish they weren’t doing any of them on your device.


How do Trojans impact mobile devices?


Trojans aren’t problems for only laptop and desktop computers. They can also impact your mobile devices, including cell phones and tablets. In general, a Trojan comes attached to what looks like a legitimate program. In reality, it is a fake version of the app, loaded up with malware. Cybercriminals will usually place them on unofficial and pirate app markets for unsuspecting users to download. In addition, these apps can also steal information from your device, and generate revenue by sending premium SMS texts. One form of Trojan malware has targeted Android devices specifically. Called Switcher Trojan, it infects users’ devices to attack the routers on their wireless networks. The result? Cybercriminals could redirect traffic on the Wi-Fi-connected devices and use it to commit various crimes.


How can I protect my computer against Trojans?


Here are some ways to help protect against Trojan malware:


  • Computer security begins with installing and running an internet security suite. Run periodic diagnostic scans with your software. You can set it up so the program runs scans automatically during regular intervals.
  • Update your operating system’s software as soon as updates are made available from the software company. Cybercriminals tend to exploit security holes in outdated software programs. In addition to operating system updates, you should also check for updates on other software that you use on your computer.
  • Protect your accounts with complex, unique passwords. Create a unique password for each account using a complex combination of letters, numbers, and symbols.
  • Keep your personal information safe with firewalls.
  • Back up your files regularly. If a Trojan infects your computer, this will help you to restore your data.
  • Be careful with email attachments. To help stay safe, scan an email attachment first. 


Here are some things you should not do:


  • Don’t visit unsafe websites. Some internet security software will alert you that you’re about to visit an unsafe site, such as Norton Safe Web.
  • Don’t open a link in an email unless you’re confident it comes from a legitimate source. In general, avoid opening unsolicited emails from senders you don’t know.
  • Don’t download or install programs if you don’t have complete trust in the publisher.
  • Don’t click on pop-up windows that promise free programs that perform useful tasks.
  • Don’t ever open a link in an email unless you know exactly what it is.


*Edited and reprinted from us.norton.com