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

Sophie Anderson Sophie Anderson How to Defend Your PC and Devices Against a Trojan Horse Virus

Short on Time? Here’s how to stay protected against a Trojan infection in 2021: 

  • A Trojan is a sneaky type of malware that masquerades as legitimate and trustworthy software so that you are fooled into downloading it onto your device. The best way to prevent a Trojan infection or get rid of existing malware on your device is to install a reliable antivirus program like Norton 360.

Remember the old tale from the Trojan War? When the Greeks left behind an enormous wooden horse and pretended to abandon the Siege of Troy and when the Trojans took it inside, the soldiers hidden inside opened the gates to the Greek army and conquered the city?

Well, like the wooden horse, Trojan viruses disguise themselves as something else to gain access to your computer or device. Trojans might use the same file name as a legitimate app so that you’re tricked into inviting them in. The hackers controlling the Trojans can then access, modify or delete your data, as well as disrupt the performance of your computer or your computer network.

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.

What Do Trojans Do?

There are many different types of Trojans, and they can do many different things. Once inside your device, a Trojan can lay low, collecting information and setting up holes or backdoors into your system undetected, or it may just take over your computer.

There are many uses or reasons for hackers to use Trojans. Some of the main uses are to:

  • Steal and Modify Data. Trojans are capable of accessing, altering, and deleting data. This is especially worrisome if you store sensitive personal or business information on your device. A Trojan is often designed to wait patiently in the background until you access your banking app or enter your credit card details. It can also be used to collect data, such as recording the keystrokes and browsing history of the sites you visit, as well as your login details and passwords for websites and banking apps. Then it sends that information on to the hacker.
  • Interrupt the Regular Performance of the System. Sometimes a hacker isn’t interested in your data but wants to use your computer to stage a massive attack on another system or to mine cryptocurrency. With the rise in cryptocurrencies, cryptojacking has become an extremely profitable activity for hackers and is rapidly growing.
  • Install More Malware and Create Backdoors. Once inside your device, Trojans will often make changes to your security system, leaving a backdoor for a hacker to use later. It will often download and install other malware onto your device, making it vulnerable to viruses and worms.

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

  • Intercepting passwords and personal details
  • Stealing bank details and credit card information
  • Gaining control of your computer 
  • Installing other types of malware

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:

  • 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.
  • Backdoor — 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.
  • Exploit — takes 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 — solicits your computer to send countless requests to a specific URL, with the aim of overloading the server and shutting down the site.
  • 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 — once the malware is on your computer, it locks you out of specific areas. The only way to regain access is by paying a ransom.

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 can look like just about anything: a computer game you downloaded a month ago, a Twitter link you clicked on that led you to a strange website, or an email attachment you downloaded that was sent from an old friend’s email address.

Unlike viruses, Trojans can’t spread on their own. Instead, they survive by staying unnoticed and hiding behind files and programs you think you can trust. Trojans rely on you to run them by mistake or through negligence. 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

Trojans take advantage of the weakest link in your computer’s defenses: you.

These forms of malware are carefully crafted to trick the user into downloading a harmful file. By carefully disguising the malware as something you might want to download, hackers try to trick you into downloading it.

Trojans are everywhere, in emails, on social media, and on the web. By clicking on a clickbait ad or checking out an attractive offer online, your device can be infected with a Trojan without you even noticing.

While not all hackers may be able to hack into the Pentagon, they understand human behavior very well. No matter how careful you are, it is almost impossible to avoid malicious links and files.

That said, there are ways to prevent contracting a Trojan infection:

  • 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 four ways to defend yourself:

  • 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.
  • 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.
  • 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.
  • 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 eyes 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

Top 3 Antivirus Programs for Defending Against Trojans

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

See Norton Deals >>>

2. Bitdefender

Top 3 Antivirus Programs for Defending Against Trojans

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 100% in all our tests.

See BitDefender Deals >>>

3. Avira

Top 3 Antivirus Programs for Defending Against Trojans

Avira (see user reviews) is also one of the most popular antivirus brands out there, and its Trojan detection and removal rates are pretty impressive. During our tests, Avira managed to identify and remove most Trojans from our test machine. The best part is that Avira offers a pretty good free version as well as excellent premium software.

See Avira Deals >>>

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. This is why an antivirus is a vital tool for filtering and removing any dangerous files that manage to get installed onto your device and stopping the damage from spreading.

Bottom line, 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.