What is a Trojan Horse and How to Protect Against It

Aviva Zacks
Posted: July 17, 2018

The first Trojan Horse existed long before computers, in the ancient Greek world of mythical battles and brave soldiers. The horse was initially an enormous wooden statue, given to the city of Troy as a gift. What the citizens didn’t know is that the giant horse was filled with Greek soldiers, ready to invade and take over.

Today, the phrase means something very different, although the concept remains similar—and equally as destructive.

What is Trojan Horse Malware?

In the modern age, a Trojan Horse is a type of malware that infiltrates your computer in disguise, then causes chaos within your system. Every type has a specific job to do, which could include the following:

  • Intercepting passwords and personal details to gain access to your accounts.
  • Stealing bank details and credit card information.
  • Gaining control over your computer network and corrupting/deleting files.
  • Collecting personal information to hijack your identity.
  • Exposing confidential details and secrets about your life.

A Short History of Trojan Horse Threats

The term first occurred in a US Air Force report, analyzing computer vulnerabilities in 1974. By 1983, it became widespread after Ken Thompson used the phrase in his famous Turing lecture, where he stated:

“To what extent should one trust a statement that a program is free of Trojan horses? Perhaps it is more important to trust: the people who wrote the software.”

During the 1980s, the Bulletin Board System—which allowed users to penetrate the web via a phone line—caused a rise in Trojan malware. As computers gained the ability to upload, download, and file share, malicious add-ons where injected onto the operating systems. Today, thousands of versions of the malware exist.

Types of Trojans

While Trojans are often labeled as viruses, this 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 role, such as the following:

  • Rootkit
    A rootkit works by concealing particular activities in your computer system. It allows malware to run undetected, to increase the length of time and amount of damage that can be achieved from one infection.
  • Backdoor
    A backdoor Trojan grants complete remote control to the owner, allowing them to edit, send, download and delete files. They are often used to hijack personal devices for criminal activity.
  • Exploit
    Exploits work by taking advantage of a security hole within your computer software. Whether in a specific app or affecting the operating system itself, they can manipulate the 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 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 to pay a fine.

While these are all common types of Trojans, their goals can 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 much, much more.

How To Spot & Avoid 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 until it’s too late. Look for these four signs that may be a warning of something sinister.

Unexplained Behavior

Any mysterious rises in CPU use are definite signifiers of a problem. If your computer has increased its processing for no reason, then a Trojan could be the answer. Use your activity monitor to check what is draining your CPU, and end the action if you find a problem. You can Google processes you don’t recognize to determine whether they’re malicious.

System Failures

If your system suddenly slows down significantly or starts crashing regularly, then it’s a sign of an issue. Use a high-quality security suite to see if you can highlight 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 dispenses 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 immediately!

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.

Tips to Avoid Getting Infected

  • Trojan Horses are often sent via email attachments in spam emails. By downloading the file, you actively infect yourself. Avoid opening 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 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 a no-cost software that is easy to download and solves a real problem for the user. While convenient, Trojan horses are known to piggyback in this type of program. Check reviews of every free program before downloading.

Protect Yourself from Trojan Threats

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

  1. Avoid Third-Party Downloads
    Any download is a potential threat. Websites, ads, and messages that contain automatic downloads often hide malware. Avoid clicking through banners and suspicious links, don’t use shortened URLs and think carefully before choosing to allow any download.
  2. Stick to Trusted Sources
    Whether it’s websites, correspondence, or software, trusted brands are always the best option. If companies are tried and tested by the general public, you’ll know if any problems have arisen. Reputation is king on the internet!
  3. Use a Firewall
    Firewalls screen data that enters your device from the internet. While most operating systems come with an inbuilt software firewall, it’s also wise to use a hardware firewall version for ultimate protection.
  4. Install a High-Quality Antivirus.
    Anti-virus and anti-malware software are your first line of defense—so it’s essential to have the best. These programs can scan your device for problems and alert you if an issue arises.

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

Best Antivirus for Trojan Horse

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! Considering this, it’s essential to opt for the best solutions that can guarantee security for your device.

Norton Antivirus

Norton is a globally recognized and trusted security brand, with an impressive detection rate of 100%. Using the LiveUpdate feature, you can scan for all currently known Trojans, quarantine infection files and delete any threats from the system. For a budget option, Norton Power Eraser promises to scan and remove malware for free!

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Known as one of the most reliable antiviruses around, BitDefender 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, which is infinitely useful!

See BitDefender Deals >>>


Although it is not the more powerful antivirus, Avast 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.

See Avast Deals >>>

Although other top-quality anti-virus and anti-malware packages do exist, they often don’t include an anti-Trojan horse element. Be sure to confirm this feature before making a purchase.

Protect Yourself from Trojan Threats Now!

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

Changing your browsing habits will help prevent an infection, but if you want to guarantee your safety then investing in a top anti-virus is the best option!

Don’t wait until disaster has struck; protect yourself from Trojan threats now.

About the Author

Aviva Zacks
Aviva Zacks

Aviva Zacks is a content manager, writer, editor, and really good baker. When she's not working, she enjoys reading on her porch swing with a cup of decaf.