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What Is a Trojan Virus and What Does it Do?

Dealing with Trojan viruses is stressful, as they can cause irreparable damage. It’s essential to have the know-how to protect yourself.

Bojan Jovanovic Image
Updated:

April 26,2022

What are Trojan Viruses?

A Trojan Horse virus, or Trojan for short, is a type of malware that takes control of your system by posing as a normal process or benign software, with the intent to inflict serious harm to your data and devices.

How Do Trojans Work?

Even though it’s commonly labeled and perceived as a virus, a Trojan cannot replicate and execute itself, as viruses do. Instead, it’s designed to trick the user into downloading and running the malware-infected file, usually via spam emails with attachments.

Whether we call it Trojan malware or a Trojan virus doesn’t make much difference regarding the potential damage this malware can cause. Trojans can remain undetected for long periods, adversely affecting your computer’s performance all the while.

Common Types of Trojan Viruses

  • Backdoor Trojans - This type of Trojan grants the hacker access to your device by creating a “backdoor”: That backdoor gives them the ability to download or steal your data, upload more malware, and execute those files at their whim. 
  • Downloader Trojans - As their name suggests, downloader Trojans download and install additional types of malicious programs to a computer. The device needs to be already infected by malware for this to work.
  • Rootkit Trojans - These Trojans aim to prevent the discovery of malware already infecting your computer by hiding it and extending its life cycle.
  • Banker Trojans - This Trojan is designed to target and steal your financial information and banking data, such as debit card and credit card information, online transactions, and bill payment data via banking systems.
  • Distributed Denial of Service (DDoS) Trojans - By performing DDoS attacks, this Trojan attacks a network or device by overloading it with traffic. These malicious attacks stem from various sources, as well as your infected computer.
  • Ransom Trojans - This type of Trojan malware prevents individuals or organizations from accessing their files. The Trojan then asks for a ransom to be paid for the compromised data to be unblocked. Of course, there’s always a chance that the hacker will never return the stolen files.
  • Spyware Trojans - Trojan spyware lurks in the background of your device and tracks everything you do. Cybercriminals can monitor your login data and gain control over the programs you’re using, take screenshots of your computer activity, and even log your keystrokes.
  • Fake Antivirus Trojans - This form of Trojan disguises itself as legitimate antivirus software. Like any other antivirus, it can discover threats and remove them, but here’s the catch: It demands and extorts money from users to do so, even if the threats are fake.

Examples of Trojan Virus Attacks

  1. Rakhni Trojan - This specific Trojan infects computers by transferring a cryptojacker tool and ransomware to devices. The cryptojacker enables hackers to hijack user devices to mine for cryptocurrency. A constant threat since 2013, this malware spreads via spam emails containing an infected PDF file. If users open or try to edit the file, the Trojan springs to action.
  2. Zeus or ZBot - This infamous malware first appeared in 2011, and its primary purpose is to steal financial data through keystroke logging, i.e., recording as you type. Zeus received massive media attention after attackers successfully hacked over 3.6 million devices in the US Department of Transportation, NASA, and the Bank of America. Due to the amount of data stolen, this became one of the most notorious Trojan malware attacks.
  3. Tiny Banker or Tinba - A reworked version of Zeus, Tinba aims to steal funds and financial data. Tinba has infected more than 20 US banking institutions since 2012. This Trojan malware example first affected Czech bank customers, before spreading worldwide.

How to Detect a Trojan Virus

The main reason Trojans have been so successful is that most victims lacked the knowledge to protect themselves. Proper vigilance is needed, as Trojan virus removal can be a pretty tricky process. Be on the lookout for these indicative occurrences on your computer or mobile device:

  • User settings being changed without the user’s input or knowledge
  • An overall decrease in device performance, such as sluggish or unresponsive behavior, and frequent program or system crashes
  • An increase in spam emails and/or browser pop-up ads

A user faced with these or similar symptoms has most likely been exposed to a Trojan attack. To remedy this, it’s recommended to carefully search through the program and file list, looking out for any unusual or unknown application and looking it up online.

While not every suspicious file will prove to be malicious, those that are will be easier to detect after you check them for Trojan associations, as other users might have faced a similar problem.

Certainly, anyone affected by this should also install and run dedicated antivirus software capable of identifying and eliminating the Trojan malware. This is the only real way to protect yourself against such incursions.

How To Protect Yourself From Trojan Viruses

The most effective defense for your computer against this malicious software is having dedicated malware removal software. While they need to be regularly updated to maintain efficiency and keep up with the latest malware definitions, these programs can provide reliable protection by identifying and preventing cyberattacks, or removing Trojan viruses if they’ve already compromised your device.

In addition to this, here are some good practices that can help you increase your malware  protection and general online safety:

  • Employ firewalls to protect your personal information
  • Use complicated passwords, with numbers and special characters, and regularly change them
  • Don’t click on any strange or unknown links, nor download suspicious files
  • Regularly back up your files
  • Do not visit unsafe websites, or click any pop-up ads offering free content
  • Keep up with the latest software updates for your operating system, as outdated versions represent a wide-open door for malicious activity.

History of the Trojan Horse

The malware was named after an event from the Trojan war. Just as the Greeks had fooled the Trojans into bringing a gifted wooden horse hiding Greek soldiers beyond their formidable walls, so too does Trojan software infiltrate a system under the guise of harmless code, only to expose it to its destructive capacity.

The first Trojan horse virus was created in 1975, as part of a test conducted for non-malicious purposes. It was only in the late 1980s that the first ransomware Trojan virus attack took place. The malware has evolved significantly since then, with over 970 million variants roaming the web right now. It’s more important than ever for users to be careful online and equip themselves with the necessary, up-to-date knowledge and protection tools.

Further Reading

FAQ
What does a Trojan virus do?

A Trojan is not actually a virus - it’s a type of malware that infiltrates your computer by tricking you into thinking it’s a legitimate program and executing it. If you don’t catch it in time, a Trojan can cause substantial damage to your files, spy on you, and steal your data.

Can a Trojan virus be removed?

There are multiple ways Trojan software can be removed. Your safest bet might be to install a good antivirus program that can identify and successfully remove Trojans. If you have more knowledge in this domain, you can try searching for the infected file and uninstalling it, but there’s no guarantee you’ll succeed.

Are Trojan viruses harmful?

Trojan Horse viruses can be very harmful, so it’s no wonder they’re considered some of the most malicious malware out there. They can infect your PC and even your mobile phone. They might appear benign at first - a simple downloadable file - but do not be fooled.

What is a Trojan virus example?

One of the most prominent examples of a Trojan virus is the infamous Emotet, whose appearance and spread date to 2018. It was used for financial information theft, and the US Department of Homeland Security labeled it as extremely menacing malware. Spam emails and phishing were utilized as a tactic to spread the infection, ultimately leading to multimillion-dollar losses.

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