What Is a Trojan horse?

A Trojan horse, or a Trojan, is a broad term used to describe any kind of malware able to infect your computer by misleading you of its true intent.


Trojans can have many different purposes. They could be designed to spy on you, hold you to ransom or, in the case of your mobile device, make money by sending SMS messages to premium numbers.


Whatever the specific end goal of a Trojan horse, the intent is always malicious and the means of infection is always to trick a user to download it. 


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Therefore, a Trojan is not technically a virus. It can’t replicate itself, instead relying on the unwitting user to execute it.


Why are they called Trojan horses?

You might be thinking, there was an Ancient Greek story about a Trojan horse, right? You are correct, and that’s exactly where the computer term gets its name from.


In the story, a hard fought war between the Greeks and the independent city of Troy came to an end when the Greeks left a ‘peace offering’ of an enormous wooden horse outside the city gates. After much debate the Trojans wheeled the sculpture inside only for Greek soldiers to emerge from within during the night and ransack the city.

How do Trojans work?

Fast forwarding from Ancient Greece to 2020, our ‘Trojan horse’ might now appear as a free game download or an interesting email attachment, hiding dangerous ‘Greek soldiers’ in the form of malware to destroy our IT environment.


A Trojan relies on social engineering - a repertoire of techniques exploiting human psychology to trick users into downloading and infecting their devices with malware.


It could come in the form of a phishing email - a message  appearing to be from a trusted source, but is purely an attempt to trick you into a malware download.


Or it could appear as ‘scareware’ - a convincing pop-up ad claiming your device is under threat and offering a handy (but secretly malware-infected) tool for your protection.


There is no limit to how creative these social engineering tactics can be. But, the intent is always the same - to mislead the user into downloading malware by pretending it is something legitimate.

What does a Trojan horse do to my computer?

A Trojan horse isn’t a single type of malware. It’s a means through which all kinds of malware, each with their own destructive and harmful missions, can infect your computer.


Here are some common types of Trojan malware and how they can impact you:

  • Banker Trojan
    As the name suggests, the aim of a Banker Trojan is to access and steal financial data such as your account information or credit or debit card details.
  • Distributed Denial of Service (DDoS) Trojan
    DDoS attacks aim to flood a network or website with traffic to overwhelm it, causing it to become unreachable. A DDoS Trojan aims to recruit your device into its army of infected devices and use it to carry out a DDoS attack on its intended target.
  • Downloader Trojan
    These Trojans can download new versions of malware to your computer.
  • Fake AV Trojan
    This is a type of scareware designed to show fake system infections until the user downloads or purchases a fake antivirus product.The proceeds go straight into the cybercriminals’ pockets.
  • Game-thief Trojan
    Online gamers can make in-game purchases such as eye-catching outfits or new weapons for their characters. This Trojan is designed to hack and steal financial information from gaming channels.
  • Infostealer Trojan
    Infostealer is designed to collect information such as contact details, usernames and passwords and upload them to a remote server.
  • Malfinder Trojan
    The Mailfinder Trojan collects and steals all of the email addresses you’ve accumulated on your device over time.
  • Ransom Trojan
    A Ransom Trojan will demand a ransom to undo the damage it has done to your device. Types of damage could include blocking some of your programs or files, slowing down your device or completely paralyzing it.
  • Remote Access Trojan (RAT)
    RATs are a type of backdoor to your device allowing hackers to do pretty much whatever they like such as send, receive or delete files.
  • Rootkit Trojan
    Rootkits are designed to hide files or activities in your computer system, making it more difficult to detect the presence of malware.
  • SMS Trojan
    The SMS Trojan can send and read text messages. Hackers can also make money by sending text messages from your mobile device to premium phone numbers.
  • Trojan IM
    An Instant Messaging Trojan will steal your logins and passwords from these platforms.

Can a Trojan infect a phone?

You may have noticed the SMS Trojan mentioned above. Unfortunately, it’s true, not even your mobile device is safe from Trojan malware. Just like on a computer, a Trojan tricks mobile phone users into downloading malware, typically through fake versions of apps.


Can iPhones download Trojan horses?

It’s quite rare for an iPhone to get infected by a Trojan.


First of all, Apple’s ‘walled garden’ approach means third-party apps must be approved and vetted through the App Store.


Secondly, apps on the iOS are ‘sandboxed’, meaning they can’t interact with other apps or gain deep access to your phone’s operating system.


However, one note of caution. If you are using a jailbroken Apple device, you won’t enjoy the same level of protection against malware. A jailbroken phone allows you to install apps usually unavailable from the official App Store. This  means Apple’s systems and processes mentioned above can no longer protect you.


Learn more about how to check for viruses on your iPhone here.

How can I protect myself against Trojans?

The only way you can fall victim to a Trojan is if you are successfully tricked into downloading one.


Perhaps, this makes it sound like protecting yourself should be easy, but that’s not entirely fair.


Cybercriminals’ sneaky tactics to trick users into downloading malware get more sophisticated and convincing by the day, with the potential to dupe even the most tech-savvy internet user.


Your best protection is to stay as informed and as alert as possible, and Clario’s here to help.


Follow these points to avoid downloading Trojans:

  • Install trusted internet security
    Your first line of defence should always be trusted, easy-to-use cybersecurity software. Clario’s solution will safeguard you against online threats, information, money and online identity theft as well as secure your browsing and Wi-Fi.
  • Keep up to date
    Be sure to keep your system’s software up-to-date. Software updates are created for a reason, usually to tighten up security.
  • Back up regularly
    While backing up your files won’t protect you from downloading a Trojan, you’ll be so glad you did should a malware attack cause you to lose anything important.
  • Be alert to email attachments
    Email attachments are a very common way for users to accidentally download a Trojan, but these ‘phishing emails’ can be difficult to identify. Always be cautious about attachments in any unexpected emails, even if they appear to be from someone you know.
  • Be alert to email links
    Untrusted links in emails can be just as dangerous as attachments, so apply the same rules here. Never click the link if something doesn’t seem quite right.
  • Be careful what you download
    It should go without saying but only download programs from publishers you know you can trust, no matter how intriguing the offer.
  • Avoid clicking pop-ups and banners
    Don’t click on unfamiliar, untrusted pop-ups warning you your device is infected or offering the magical program to fix it. This is a common Trojan horse tactic.

What should I do next?

A Trojan horse is any type of malware able to infect your device by misleading you of its true intent. Once you fall for it, the people behind it begin to unleash all kinds of damage and destruction on your device.


If you've read this article, you're already taking positive steps to avoid downloading a Trojan.


But you don't have to defend your devices all by yourself. Sign up for Clario's simple, all-in-one cybersecurity software and get all of your online protection and privacy needs covered in one subscription.


Learn more about Clario’s solution now.

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