Identifying and Avoiding a Trojan Horse Virus

Malware is difficult to deal with, but it's even harder to purge when you don't even realize you've downloaded it. This is why some hackers turn to Trojan horses malware: viruses that users download from a source that appears to be safe.

These viruses then go on to damage their computer, affecting the device's performance and harming files, potentially without the user ever realizing that they downloaded malicious software. The key to Trojan horses is that they are sneaky, which makes it all the more important that users are aware of what to watch out for.

What is a Trojan horse virus?

A Trojan horse, also known as a Trojan, refers to seemingly-legitimate malicious code. Much like the famous wooden horse that was cleverly used by the Greeks to get into the City of Troy during the Trojan War, a Trojan horse virus tricks users by appearing as a secure application before loading and executing malware.

Though it’s often referred to as a virus, Trojan malware technically isn’t; a virus can execute and replicate itself, whereas a Trojan horse needs an executor. Regardless, most people understand both terms to mean the same thing.

A Trojan, by design, attacks the files and functions of your computer. It has the capacity to delete, block, modify, or copy data. Its general goal is to disrupt a device’s performance; this may go as far as disrupting an entire computer network. Admittedly, the term “Trojan horse malware” is better used to describe the delivery method of malware than a specific type of malware—there are numerous kinds of Trojan malware, and what they all have in common is the way they’re spread and executed.

How does it work?

Trojan viruses are tricky. They work by taking advantage of weak security on a user’s computer or device to appear as a form of malware, usually from a trusted source or location. Emails, for example, are ideal vehicles for Trojan horse malware because the Trojan can be sent as an attachment from a fake sender address. The user receives the email, believes it to be safe, and downloads the attachment.

If the user downloads and opens the attachment, unbeknownst to the user, the Trojan virus is installed and activated. The victim actually ends up serving as the executor or activator that the Trojan needs. The Trojan infects and damages files or worse. There are many different kinds of Trojan horse malware, though, and each works in a slightly different way.

Is a Trojan virus harmful?

Yes, Trojan viruses are malicious programs. Whether or not users realize that they have one on their device, Trojans cause damage to files, hardware, and data on a device.

Different kinds of Trojan horse viruses

Backdoor Trojans

Backdoor Trojans manipulate your computer into becoming a gateway for further attacks. They upload malware onto your operating system that makes it vulnerable to attack and used in a system to attack others. Your device becomes harmed, and through it, other computers become affected, too.

Backdoors allow code or commands ultimately executed on your computer. They can also monitor your Internet traffic without your knowledge.

Distributed denial-of-service Trojan horse virus

A distributed denial of service attack—otherwise known as a DDOS attack—attacks a computer or system of computers by flooding the server with more requests that it can possibly handle. Thus, it effectively shuts down the system.

Distributed denial of service attacks require a number of other manipulated computers, however, in order to deliver a successful assault. Here, distributed denial-of-service Trojans come into play. The distributed denial-of-service Trojans use a backdoor method to get onto a victim’s computer.

Once activated, the infected computer can serve as part of a botnet in another attack. That potentially renders an entire network inaccessible.

Banking Trojans

Banking Trojans focus on using phishing techniques in order to get users’ banking login credentials. They're one of the most common types of Trojans. The user might receive an email or text telling them they need to log into their account.

When they attempt to log in to their account, they are redirected to a phishing site. This false site then collects the information they enter without their knowledge, leading to identity theft.

Downloader Trojan horse virus

A downloader Trojan installs itself into a computer system remotely. Once the device connects to the Internet, then the Trojan can download malware onto the user’s computer. Downloader Trojans are frequently sent out as seemingly-legitimate files in spam emails, but it’s the same story: once the user downloads or opens the email attachments, the downloader Trojan gets installed onto the device.

Antivirus Trojans

If you’re someone who is particularly careful about protecting your device from computer viruses, you’ll want to stay alert for antivirus Trojans. They prey on the diligent, falsely alerting users of viruses that are on their devices and urging them to buy an antivirus program to protect themselves. However, the antivirus program they urge users to buy is not legitimate. Instead, users have just allowed an antivirus Trojan to slip onto their device instead. It will only cause more problems.

Therefore, if alerted out of nowhere when browsing the web of a computer infection, you may want to ignore the claim. If you’re concerned, run a scan with an official antivirus program like Norton.

Keylogger Trojan horse virus

Keyloggers, as the name implies, log every stroke you make on your keyboard. When one of these gets on your computer, the hacker is able to essentially monitor everything you do and collect records of everything you type. This includes all passwords, bank account numbers, email addresses, and messages.

This makes keyloggers incredibly dangerous to device users, whether you prefer a laptop or a mobile device. Keylogger Trojans, like all other kinds, can get on your device easiest if your antivirus software is outdated.

How to detect Trojan viruses

Run a scan with your antivirus software program of choice to know whether or not your device infected by a Trojan virus. However, without a scan, these are a few symptoms that could indicate you have a problem.

Your device runs slower than usual

Trojans take up a lot of your computer's processing power. If you find that your computer isn't loading as quickly or it seems to have trouble with basic tasks, there might be Trojan malware hiding somewhere in your device.

You get a lot of pop-ups

Frequent pop-ups are another indicator that you have a malware infection. These can be on your desktop, claiming you need to update your computer's security, or they could be on the Internet as soon as you log on. Either way, if you find yourself closing out of multiple pop-ups every time you open your laptop, consider checking for Trojan malware.

Your computer seems to have a mind of its own

When dealing with Trojan malware, users may notice their devices acting unusually. It might restart or shut down on its own. The malware changes or deletes files without action on your part. If your computer generally just seems off, a Trojan might be behind it.

Prevent Trojan horse viruses

With any kind of malware, including Trojan horse malware, you can lower your risk level if you follow a few protective steps. First and foremost, make sure that you have a strong antivirus program that is up-to-date and thorough.

Furthermore, don't put off updates to your antivirus software or your computer. Both of these things lowers the protection on your device. It also increases the chances that malware or a virus could slip through.

Use your antivirus program to run scans. It ensures that you don’t have any malware, Trojan or otherwise, hiding in your device. Antivirus software can detect and remove the malicious software, and it can also seek out any other security threats to your device.

How to prevent malware attacks

In general, it’s a good habit to set strong, unique passwords on every one of your accounts. Create new passwords for each account rather than reusing passwords on multiple sites. As tempting as it is, this makes it far easier for hackers to take advantage of you.

If you’re someone who doesn’t have the best memory or if you hate coming up with your own passwords, try a password manager to create and save strong passwords. You should also change your passwords every few months to be completely safe.

Keeping an eye out for suspicious emails, email attachments, text messages, or social media DMs is crucial when it comes to preventing Trojan horse downloads. Check out what to look out for in phishing emails and never open messages from people you don’t know or trust.

Another excellent safety practice is backing up your files. Though it can’t prevent malware from getting on your device, if your files are affected by a computer virus, computer worm, or Trojan, you will at least have a backup copy to restore your data.