A Trojan, or Trojan horse, is a type of malware that conceals its true content to fool a user into thinking it's a harmless file. Like the wooden horse used to sack Troy, the "payload" carried by a Trojan is unknown to the user, but it can act as a delivery vehicle for a variety of threats.
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Types of Trojan viruses
Some of the most common types of Trojan virus include:
Backdoor Trojans- This type of Trojan allows hackers to remotely access and control a computer, often for the purpose of uploading, downloading, or executing files at will.
Exploit Trojans-These Trojans inject a machine with code deliberately designed to take advantage of a weakness inherent to a specific piece of software.
Rootkit Trojans-These Trojans are intended to prevent the discovery of malware already infecting a system so that it can affect maximum damage.
Banker Trojans-This type of Trojan specifically targets personal information used for banking and other online transactions.
Distributed Denial of Service (DDoS) Trojans- These are programmed to execute DDoS attacks, where a network or machine is disabled by a flood of requests originating from many different sources.
Downloader Trojans-These are files written to download additional malware, often including more Trojans, onto a device.
How to recognize and detect a Trojan virus
Because Trojans are used as a delivery device for a number of different types of malware, if you suspect your device may have been breached by a Trojan, you should look for many of the same telltale signs of malicious software. These may include:
Poor device performance- Is your computer or mobile device running slowly or crashing more frequently than normal?
Strange device behavior- Are programs running you didn’t initiate or are other unexplained processes being executed on your device?
Pop-up and spam interruptions- Are you noticing an uptick in the number of interruptions from browser pop-ups or email spam?
If your device is exhibiting these symptoms, it’s possible a Trojan virus has managed to sneak its payload onto your computer. Try searching your computer for any programs or applications you don’t remember installing yourself. Enter any unrecognized file names or programs into a search engine to determine if they are recognized Trojans.
Finally, if you haven’t already, scan your computer with antivirus software to see if it has uncovered a malicious file.
Examples of Trojans
Zeus- Also known as Zbot, Zeus is a successful Trojan malware package with many variants used to carry out a number of different types of attack. It’s perhaps most well-known for its successful hack of the U.S. Department of Transportation.
Wirenet- Wirenet is a password-stealing Trojan notable for being among the first to target Linux and OSX users, many of whom were migrating from Windows operating systems based on perceived security flaws.
Mobile banking Trojans- Webroot has documented a number of Trojans written to target mobile banking apps for the purpose of stealing login credentials or replacing legitimate apps with malicious ones.
Protect your computer from Trojan horse threats
As with protecting against most common cybersecurity threats, effective cybersecurity software should be your front line of protection. An effective internet security solution should run fast, frequent scans and alert you as soon as a Trojan virus is detected.
If you're reading this because it's already too late, see our page on removing malware infecting your computer. If you're reading this to stay safe from these types of attacks in the future, there are a few best practices in addition to installing cybersecurity software to help keep yourself safe:
Never download or install software from a source you don’t trust completely
Never open an attachment or run a program sent to you in an email from someone you don’t know.
Keep all software on your computer up to date with the latest patches
Make sure a Trojan antivirus is installed and running on your computer
Read more about Trojan viruses
To stay up to date with emerging Trojan viruses and other online threats, stay tuned to the Webroot Threat Blog.
It’s where our team of dedicated threat researches keeps you informed about developing threats, trends in cybercrime, and other news from around the cybersecurity industry.
FAQs
A Trojan is a sneaky type of malware that infiltrates devices by camouflaging as a harmless program. Trojans are hard to detect, even if you're extra careful. That's why antivirus software is necessary if you want to protect yourself from this type of malware.
How to protect trojan virus? ›
Protect your computer from Trojan horse threats
- Never download or install software from a source you don't trust completely.
- Never open an attachment or run a program sent to you in an email from someone you don't know.
- Keep all software on your computer up to date with the latest patches.
A Trojan Horse (Trojan) is a type of malware that disguises itself as legitimate code or software. Once inside the network, attackers are able to carry out any action that a legitimate user could perform, such as exporting files, modifying data, deleting files or otherwise altering the contents of the device.
What should I do if I get a Trojan virus? ›
Unfortunately your other choices are limited, but the following steps may help save your computer and your files.
- Call IT support. ...
- Disconnect your computer from the Internet. ...
- Back up your important files. ...
- Scan your machine. ...
- Reinstall your operating system. ...
- Restore your files. ...
- Protect your computer.
Follow these steps:
- Step 1: Disconnect internet. Before you start removing the Trojan, make sure that you disconnect from the internet. ...
- Step 2: Launch antivirus program. ...
- Step 3: Remove Trojan in Safe Mode. ...
- Step 4: Perform system recovery. ...
- Final option: Reinstall Windows 11.
How can you tell if you have a Trojan virus?
- Your computer is running slower than usual. ...
- Unauthorized apps are appearing on your device. ...
- You experience constant operating system crashes and freezes. ...
- You experience an increasing number of internet redirects. ...
- You experience frequent pop-ups. ...
- Applications won't start.
These programs can cost you money - by sending text messages from your mobile device to premium rate phone numbers. Trojan-Spy programs can spy on how you're using your computer - for example, by tracking the data you enter via your keyboard, taking screen shots, or getting a list of running applications.
How long does a Trojan virus last? ›
A Trojan horse virus can often remain on a device for months without the user knowing their computer has been infected. However, telltale signs of the presence of a Trojan include computer settings suddenly changing, a loss in computer performance, or unusual activity taking place.
How to get rid of trojan virus for free? ›
The best way to clean up a Trojan infection is to use Malwarebytes' free trojan scanner, and then consider Malwarebytes Premium for proactive protection against future Trojan infections. Malwarebytes Premium will initiate a scan for Trojans and then remove Trojans so they can't cause further damage.
How harmful is a Trojan? ›
The aftermath of a Trojan attack can be devastating. Trojans can cause data loss, financial loss, and even identity theft. Understanding the threat that Trojans pose is the first step to securing your system and valuable personal data against these malicious programs.
By removing the internet connection, you prevent an attacker or virus from being able to access your computer and perform tasks such as locating personal data, manipulating or deleting files, or using your computer to attack other computers.
What is the best Trojan remover? ›
Bitdefender is the best antivirus for Trojan detection and removal. It has a well-rounded security system to protect your device from Trojan malware. Additionally, Bitdefender offers a free version.
What does the Trojan virus look like? ›
Trojans can look like just about anything, from free software and music, to browser advertisem*nts to seemingly legitimate apps. Any number of unwise user behaviors can lead to a Trojan infection.
Are Trojan viruses hard to get rid of? ›
Installing and using a trusted antivirus solution is also one of the top ways to get rid of trojans. An effective antivirus program searches for valid trust and app behavior, as well as trojan signatures in files in order to detect, isolate and then promptly remove them.
Which antivirus can remove Trojan? ›
Don't forget about protecting your Android phone and tablet. Avast's free antivirus tool for Android eliminates trojans and other malware threats while keeping your Wi-Fi connection secure. iPhones and iPads are also susceptible to malware.
Can Trojan virus control your phone? ›
Impact. Once the trojan is installed on the device, it silently performs its actual, unauthorized functions, which may range from harvesting personal data from the device, to sending premium SMS messages or intercepting SMS messages, connecting the device to a botnet and so on.
Can Trojans hide from antivirus? ›
Yes, malware can hide itself and antivirus and other protection programs may not catch it.
Can Trojan virus be removed by Windows Defender? ›
If Windows Defender finds a trojan horse, it will quarantine and remove the trojan horse automatically, so you shouldn't have to confirm or perform any actions.
Can you recover from a Trojan virus? ›
Trojans are malicious programs that infect computers by misleading users of their actual intent. These Trojans can lead to a huge data loss in the computer/PC that they affect. If a Trojan affects your PC and you have lost your files, then do not be worried- it is possible to recover files from the Trojan virus.
Can Trojan virus spread through WIFI? ›
Yes, malware can spread through Wi-Fi and infect interconnected devices. In addition, Wi-Fi provides a lucrative attack vector (pathway) that cybercriminals use to propagate malware. As an attack vector, Wi-Fi networks can be easy to exploit, and an attacker can target many vulnerable victims at once.
