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How to Defend your PC and Devices Against a Trojan Horse Virus

Much like the Trojan Horse in Greek mythology, a Trojan Horse virus is a type of malware that infiltrates your computer in the disguise of a harmless file. It then lies in wait only to harm your PC and devices when you least expect it.

Most Trojans aim to take control of your computer and steal your sensitive data, while acting as a gateway to allow even more malware to infiltrate. So how do you quickly spot the telltale signs of a Trojan infection before it’s too late, while defending your PC and devices against these malicious attacks?

We’ll show you.

Quick List:

What do Trojans do?

In a nutshell, each Trojan Horse is created with a specific job in mind, including any of the following:

  • Intercepting passwords and personal details to gain access to your accounts
  • Stealing bank details and credit card information
  • Gaining control of your computer network and corrupting/deleting files
  • Collecting personal information in order to hijack your identity
  • Exposing your most confidential details

Types of Trojan Horses

While Trojans are often labeled as viruses, this definition is not technically correct. A computer virus will attempt to spread the infection wherever possible, whereas a Trojan is an individual program with a specific task, such as any of the following:

  • A Rootkit
    A rootkit works by undermining your computer’s system activities. It allows malware to run undetected, to increase the length of time and amount of damage that can be achieved by one infection.
  • A Backdoor
    A Backdoor Trojan grants complete remote control to the operator, allowing them to edit, send, download and delete files. They are often used to hijack personal devices for criminal activity.
  • An Exploit
    Exploits work by taking advantage of a security loophole within your computer software. Whether in a specific app or affecting the operating system itself, they can manipulate a vulnerability to gain direct access to your files.
  • DDoS
    Standing for “Distributed Denial of Service,” these Trojans will solicit your computer to send countless requests to a specific URL, with the aim of overloading the server and shutting down the site.
  • Spyware
    Spyware aims to intercept your personal information. This goal is achieved by copying your files or using a screen or keylogger to record what you type and which websites you visit.
  • Ransomware
    Ransom attacks are often carried out using a Trojan. Once the malware is on your computer, it locks you out of specific areas. The only way to regain access is by paying a fine.

While these are all common types of Trojans, their goals vary considerably. Most aim to steal information for financial gain. This can include bank information, online gaming details, IM log-ins, personal contacts, phone data and more.

How to Spot Trojans

Trojans are incredibly good at hiding. The whole point of their existence is that they trick users into installing them, and then work behind the scenes to achieve their aim. If you fall victim, you may not even realize it until it’s too late.

Look out for the following four signs, which may be a warning of Trojans attacking your computer:

Unexplained Behavior

Any mysterious increase in CPU usage is definitely a red flag. If your computer has increased its processing activity for no reason, then a Trojan may be the reason. Use your activity monitor to check what is draining your CPU, and end the action if you find a problem.

You can Google any processes you don’t recognize to determine whether they’re malicious or just part of normal system activity.

System Failures

If your system suddenly slows down significantly or starts crashing regularly, then there’s something wrong. Use a high-quality security suite to see if you can identify the problem.

Increase in Spam

Pop-ups, annoying adverts, and a general rise in spam on your machine could indicate an adware Trojan. This malware type uses infected ads to spread the virus further. Avoid clicking on anything that looks suspicious!

Unidentified Programs

If you spot an app or program that you didn’t download, it’s a cause for concern. Google the name to ensure it’s not an important part of the operating system. If it’s not— delete it immediately!

Tips to Avoid Getting Infected

As the online world becomes increasingly streamlined, so do Trojans. There’s no guarantee you’ll notice a problem, so it’s also essential to know how to avoid contracting one in the first place:

  • Trojan Horses are often sent via email attachments in spam emails. By downloading the file, you actively infect yourself. Avoid opening any emails from people you don’t know.
  • Fake software is another common transmitter. The victim will choose to install a program, without realizing it’s transporting a Trojan. Only download well-reviewed apps and files from trusted sources to avoid this issue.
  • You don’t always have to download a Trojan virus actively. Simply visiting an infected website is enough to transfer the infection. Avoid clicking through banner ads and visiting random sites to reduce the risk.
  • Freeware is no-cost software that is easy to download. While these free programs are convenient, Trojan horses are known to piggyback on them. Do some independent research and read reviews on any free program you’re thinking about installing before downloading them.

Protect yourself from Trojan Threats

Fortunately, although the problem is widespread, solutions do exist. By taking pre-emptive steps to protect yourself, you can stay safe from Trojan threats.

Here are five ways to defend yourself:

  1. Install a High-Quality Antivirus
    Antivirus and anti-malware software should be your first line of defense — and it’s essential to install something robust enough for the job. These programs scan your device for problems and alert you if an issue arises. Some will also quarantine and delete any threats from your device.
  2. Avoid Third-Party Downloads
    Any download is a potential threat. Websites, ads, and messages that contain automatic downloads often hide malware. Avoid clicking through to any banners and suspicious links, don’t use shortened URLs and think carefully before allowing any download.
  3. Stick to Trusted Sources
    Whether it’s a website, correspondence, or software, always stick to trusted brands. If companies are tried and tested by the general public, you’ll know if any problems have arisen. Reputation is king on the internet so always check independent reviews as well.
  4. Use a Firewall
    Firewalls screen data that enters your device from the internet. While most operating systems come with a built-in firewall, it’s also a good idea to use a hardware firewall for full protection.

Trojan horses are a complex form of malware, so you need more than two eye to spot them. Using security software like antivirus, anti-malware and firewalls will give you an extra layer of protection.

Top 3 Antivirus Programs for Defending Against Trojans

Not all antivirus software has the capability to detect Trojan Horses. In fact, many free or low-cost options may actually be malware in disguise! That’s why it’s essential to opt for the best solutions that can guarantee top security for your device.

Here are our recommendations:

1. Norton Antivirus

Norton (see user reviews) is a globally recognized and trusted security suite with an impressive 100% detection rate. Using the LiveUpdate feature, you can scan for all currently known Trojans, quarantine infection files and delete any threats from the system.

For those on a budget, Norton Power Eraser scans and removes malware for free!

See Norton Deals >>>

2. BitDefender

Known as one of the most reliable antivirus programs around, BitDefender (see user reviews) excels in identifying malware and restoring problems quickly. It offers real-time protection and web filtering, boasting a detection rate of 99.9%. The company also provides a specific tool for aggressive Trojan threats.

See BitDefender Deals >>>

3. Avast

Though not necessarily the most powerful antivirus we’ve tested, Avast (see user reviews) offers a budget-friendly free version that comes complete with a Trojan-removal tool. The app is rated “excellent” by industry experts, and also provides browser cleaning and password security features.

Get Avast Now >>>

Although other top-quality antivirus and anti-malware packages do exist, they often don’t include an anti-Trojan Horse element. Be sure to confirm that the security suite you’re looking at includes this feature before purchasing.

Protect yourself from Trojan Threats Now!

Trojan Horses have been around nearly as long as the internet itself. They can be more destructive than most types of malware because they’re so difficult to spot.

Changing your browsing habits will help prevent an infection, but if you want to really boost safety, then investing in a top quality antivirus with a decent Trojan removal tool is the best way to go.

About the Author

Sophie Anderson
Sophie Anderson
Cybersecurity researcher and tech journalist

About the Author

Sophie Anderson has spent the last 10 years working as a software engineer for some of the biggest tech companies in Silicon Valley. She now works as a cybersecurity consultant and tech journalist, helping everyday netizens understand how to stay safe and protected in an online world.