What Is a Trojan Horse in Computer Terms?


Have you ever wondered, “What is a trojan horse?” or “What does the term “trojan horse” mean in the context of computers?” That’s most likely because there’s a lot of doubt about whether trojans are malware or a form of virus, and people often mix viruses, trojans, and other forms of malware in posts.

But don’t be concerned. We’re here to lift the veil of mystery and expose all there is to know about trojan viruses, trojan bugs, and trojan horses. This involves looking into the following:

    • In programming language, what is a trojan horse? (and where the name came from),
    • Why do poor guys like trojans?
    • The ten most famous trojan forms,
    • What to check for to see if your system is compromised, and how to keep trojans from infecting your computer

What Exactly Is a Trojan Horse?

Malicious software (malware) that is disguised to appear like a legitimate computer programme, application, or file is referred to as a “trojan horse” (or simply “trojan” for short). It is specified as follows by the National Institute of Standards and Technology (NIST):

“A computer program that appears to have a useful function, but also has a hidden and potentially malicious function that evades security mechanisms, sometimes by exploiting legitimate authorizations of a system entity that invokes the program.”

A trojan creator (hacker) creates software that has a deceptive name or infects a legitimate application with harmful trojan malware. The trojan malware will hide in a variety of places, like directories, directories, photographs, videos, slideshows, and so on.

Cybercriminals use this ruse to lure unsuspecting consumers into installing their malicious applications and then infect their computers with malware.

What’s the Difference Between Trojans, Worms, and Viruses?

Let’s start by emphasizing that these are all distinct (but related) threats. To achieve their destructive ends, these three kinds of malicious code take separate paths.

Unlike a computer worm, which spreads on its own, a conventional trojan requires a user’s manual intervention to enter (and activate) a host computer. Until a user taps, downloads, or installs the trojan, it remains inactive in the infected software.

Orthodox trojans, unlike viruses, are incapable of self-replication. They remain local in the same tainted program in which the author of the program has stored it. That means it can’t damage other programs or applications.

Classic trojans, on the other hand, are often paired with viruses or worms. These hybrid trojans self-replicate and spread their payloads to all other attached IoT computers, apps, USB drives, and web browsers.

The Origins of “Trojan Horse” in IT Security

The name trojan horse refers to a large wooden horse that the Greeks used during the Trojan War.

To recap, the Greeks built a massive wooden horse, buried soldiers inside, and pretended to flee Troy during the Trojan War. The Trojans, the citizens of Troy, carried the wooden horse into the city as a token of their triumph. However, Greek soldiers emerged from the wooden horse at night and opened Troy’s gates, allowing the remaining Greek army to invade and defeat the settlement.

Because of the malware’s misleading appearance, the trojan horse was given this name in the computing world. The user willingly installs an application, believing it to be a harmless, usable program, not realizing it is infected with malware.

Why Attackers Use Trojans

Infected computers are harmed in many of the same ways as other forms of malware. They also play a role in assisting cybercriminals:

    • For ransomware attacks, steal and encrypt the info.
    • User IDs, email addresses, passwords, security questions, PINs, and other login information are stolen.
    • To send phishing emails in your name, gain access to email clients.
    • To commit financial theft, steal financial information such as credit card numbers or bank account numbers.
    • To carry out man-in-the-browser attacks, gain access to web browsers.
    • Take your publicly identifying information (PII) in order to steal your name.
    • Man-in-the-middle assaults should be carried out.
    • Steal other kinds of private, critical, or classified information through engaging in espionage (such as political data, proprietary research, trade secrets, and military-related data).

Server-side attacks: While most trojans are designed to threaten end-user computers rather than servers (websites) or networks, the dangers they face are not limited to that. When trojans infect user computers to form a botnet army, many large forms of cyber attacks against websites and servers — such as DDoS attacks, brute force attacks, man-in-the-middle attacks, and so on — occur.

Trojan Horse Invasion Techniques

Let’s take a look at how the attackers get the trojan horse into a computer.

Compromised Software and Apps

Hackers infect legitimate executable files (.exe) with trojan malware or create fresh infected applications with a misleading name. Consider the following scenario:

    • Skyp3.exe (instead of Skype.exe),
    • $recyble.bin, (instead of Recycle bin)
    • Instagram, (Instead of Instagram)
    • TikTok-online, (Instead of Tik-Tok)
    • Nort0n antivirus (Instead of Norton Antivirus)

If you will see, these titles are written in such a manner that unwary people will believe they are genuine applications, games, or files and will download them. Hackers also make infected products available for free download to entice unwitting users into installing them. The trojans will then take possession of the users’ computers after they install the malicious objects.

Phishing Emails

Hackers use phishing email links and attachments to spread various forms of malware. Phishing emails seem to be from reputable outlets such as your bank, an eCommerce firm, acquaintances, family, your professional circle, or some other legitimate company, but they aren’t.

For eg, you can believe the email below is from PayPal and the attachment is a harmless pdf receipt. If you download it, though, the trojan will infect your computer.

Advertisements and Pop-Up Messages

When users visit a spammy or corrupted website, they are bombarded with enticing ads, bogus virus infection threats, enticing gossip stories, and surprising news, among other things. The trojan is mounted in the user’s browser when they press on those pop-ups.

Fake Updates

As users want to view any video or file on the internet, the website refuses them to access and directs them to a link where they can update the most recent version of a media player, browser, or other forms of apps. When they uninstall the program from the connection given in the post, however, a trojan malware-infected version of the app is downloaded onto the users’ devices.

The 10 Common Types of Trojan Horses

The payload is designed by the trojan author to manipulate the host computer in a particular way. Trojans are usually classified according to their duties. While all trojans are created differently, the following are some of the most popular forms of trojan malware we’ve seen on the internet in the past.

Botnet Trojans

These trojans are intended to disperse their payloads to other attached computers, causing them to enter a botnet. Botmasters are the creators of the trojans, and they use C&C servers to monitor all infected computers. The botmaster uses a vast number of compromised computers that have joined the same botnet to carry out numerous cyber attacks (DDoS attacks, brute force attacks, etc.).

Deceptive Antivirus Trojans

Users get pop-up messages telling them that their computers have been compromised with malware. Once customers are persuaded that their computers are compromised, the attackers sell them bogus antivirus apps with malware preloaded on it or bill for virus removal services.

Email Corrupting Trojans

These trojans are made to access the hosts’ email clients. They can:

    • Intercept email communications,
    • Send the victims’ contact lists to the attackers,
    • Send phishing emails on behalf of the victims (without the victims’ knowledge) and erase the emails from their sent folders.

Backdoor/Remote Access Trojans

These trojans give remote access to the infected devices to cybercriminals. With this comprehensive access, trojan authors can:

    • Access, modify, and transfer files,
    • Send and receive information with other connected IoT devices,
    • Reboot the system,
    • Install or uninstall software, and
    • Get many other such privileges.

Ransomware Trojans

These trojans are capable of encrypting, locking, and deleting info. They even have the ability to lock vital applications or even the entire operating system. Extortion money is demanded by the trojan writers in exchange for access to the victims’ records, files, programs, or the whole machine. (However, as you would expect, even though certain victims pay, the bad guys might not follow through with their promise.) If the victims do not pay the ransom, the attackers will threaten to reveal their personal details or release classified information.

Vulnerability Finding Trojans

After infiltrating a target’s laptop, trojans look for flaws in the operating system, applications, and software that have been mounted. After that, the trojans send the vulnerability lists to the trojan operators. In most cases, those flaws can be detected in older versions of software. Based on the essence of their unpatched glitches, this knowledge aids hackers in devising new ways to manipulate the computers (and other devices with similar vulnerabilities).

Download Enabler Trojans

When a victim’s computer connects to the internet, these trojans import other forms of malware onto their computers without their knowledge.

Spyware Trojans

Spyware trojans (also known as spyware) are secret programs that enable attackers to monitor the activities and behaviors of their targets. This covers everything from what users type on compromised computers to the data they send over the internet (such as personal information, financial data, login credentials, etc.). The details will then be used by spyware users to commit identity theft, financial fraud, or ransomware attacks.

File Transfer Protocol Trojans

Attackers use trojans to open port 21 on the host computer, allowing them to access files via the file transfer protocol (FTP). After gaining access to the FTP directories, the attackers will remotely upload and copy malicious files to the victims’ computers.

Security Software Disabler Trojans

Without the users’ awareness, these trojans turn off, disable, or remove computer security applications such as antivirus, antimalware, and firewalls. As a result, the attackers disable antivirus protection before they can identify the trojan and its payloads. Users believe that their computers are already shielded by the security software, and they blindly trust compromised applications without question.

8 Symptoms That Your Computer or Device Could Have a Trojan Horse

So, how can you tell if your computer or laptop has been compromised with a trojan horse? For instance, the first response is to search for an anti-malware scanner (and certain antivirus programs). If your computer is infected with a trojan or some form of malware, the symptoms are always the same:

  1. Antivirus and anti-malware software is turned off: Your antivirus software can be disabled or even uninstalled without notice.
  2. High Latency and Load Speeds: The interface becomes sluggish and slows all of a sudden. You will get notifications that your computer does not have enough memory to complete tasks or run programs.
  3. Freezing Screen: You might also get the infamous “grey screen of death” if the screen freezes up entirely.
  4. Cursor Movements That Aren’t Normal: The mouse cursor begins behaving strangely. This could entail running automatically, in different directions, or at different speeds. You may not be able to shift or manage it at all in some situations. The cursor can vanish at times, but you may find certain events on your computer, such as programs or browsers that open automatically (as if someone is operating your device from a remote place)
  5. Unexpected Pop-ups: Unwelcome pop-ups begin to appear on your computer. This can range from regular malware and app upgrade warnings to commercials and messages urging you to install unknown software programs.
  6. Automatic Page Opening: Several obscure websites open in your window as soon as you connect to the internet or open a browser. When browsing the internet, you may be diverted to an obscure spammy website.
  7. Unknown Extensions Appear in Your Browser: Your web browser will have some unknown extensions added. Type chrome:/extensions/ in Chrome’s address bar or about: addons in Firefox’s address bar to see what extensions you have enabled. To manage add-ons in Internet Explorer, go to the main menu and select Manage Add-ons.
  8. Unknown Programs in Task Manager: If you open your task manager window (by pressing Ctrl+Alt+Delete), you will find that some unknown programs and applications are working.

How to Protect Your Device from Trojan Horses

Beware of Phishing Emails

Phishing emails are often used by attackers to spread trojan horse malware. To stop uploading or installing a trojan by mistake, follow these steps:

    • Make sure you and your colleagues know how to spot a phishing note. Take a look at these two simple articles: Phishing email scams and how to tell if an email is bogus.
    • Downloading an email file from an anonymous sender is not a good idea. Additionally, before installing something, make sure to check all email attachments with anti-malware apps (even from senders you know).
    • To find out where the links in the email directly redirect to, move your cursor over them. You may also inspect the connections by right-clicking on them and selecting Inspect. The website to which the provided connection will take you is the link you will see after a href=”

Regularly Scan Your Devices with Anti-Malware Software

The bulk of trojan malware can be detected and removed using security tools and firewalls. They will even alert you whether you visit a malicious or spammy website or download an infected file from the internet.

Be Careful When Downloading Anything from the Internet

You’re already aware that trojan horses imitate legitimate applications in order to trick users into installing them. As a result, you must exercise extreme caution when accessing something from the internet. Scrutinize all you get from the internet.

Apps: Downloading obscure apps can be avoided. When you’re looking for an app and come across a slew of those with slightly different names, do a quick internet search to find the official name of the app you want to install.

Let’s presume you want to use Zoom for video conferencing. Zoon-online, ZoomMeeting, GetZoom, Zoom Calling, Zoom Video Calling, and other applications could be available. You’re not sure one of these is genuine, however. Before downloading an app on your smartphone, go to the app’s official website and look up the app publisher’s name in the app store to see which one belongs to the Zoom network.

Apps: If you’re installing apps, look for the publisher’s name in the protection window, then do a fast Google search and read the feedback. If the publisher’s name seems to be Unknown, do not install the software. When the name of the software publisher is written as Unknown, it means they are not using a code signing certificate. As a result, such software should not be assumed to be trustworthy in terms of its credibility and validity.

Code signing certificates are used by legitimate developers and publishers to shield their apps from tampering. The certificate authority (CA) that issues the certificate goes through a thorough vetting process to ensure that the app publisher is legitimate before issuing the certificate.

Always Store Backups on Third-Party Cloud Platforms:

Often back up your data to a third-party cloud service like Google Drive or Dropbox. In the event of a crash or a cyber attack, this will assist you in recovering your files. If you have a current data archive, you can recover anything if a trojan corrupts, encrypts, or deletes your data. For ransomware threats, backups are the only option. Until transferring files to the backup folder, run them via anti-malware tools.

Keep Your Systems Patched and Up to Date

Keeping the operating system and other applications up to date is the safest protection against multiple forms of ransomware, including the vulnerability detecting trojan. Updates aren’t just about improving the software’s appearance and features. The publishers repair the old versions’ security flaws and release the modified edition. Hackers create ransomware that can take advantage of the old version’s flaws. As a result, it’s critical to always upgrade the most recent version of the operating system, applications, and apps as soon as they become usable.

Wrapping Up on Answering “What Is a Trojan Horse?”

You can’t get a trojan horse into your machine until you manually download it. So, if you import something from the internet, be cautious. If you come across any device, service, application, freebies, or commercials online that seem to be too good to be real, trust your instincts and don’t download them.

If you get an unsolicited communication offering you a reward (lottery win, grand prize, promotional goods, etc. ), consider why you were chosen. How many people do you meet who have made millions of dollars just by playing video gaming or gambling? If you get a notification that you must use such applications to access content (such as a flash player or other media player), do a fast search for that software and read consumer feedback. Also, even if it is a well-known program or browser plugin, instead of clicking on the connection given in the pop-ups, install it from their official website.

Melina Richardson
Melina Richardson is a Cyber Security Enthusiast, Security Blogger, Technical Editor, Certified Ethical Hacker, Author at Cybers Guards. Previously, he worked as a security news reporter.