What is Trojan Horse (Trojan) Virus? How can you remove trojans from computer?

• May 3, 2023June 8, 2023

A Trojan horse virus is a type of malware, such as malware or spyware. It infiltrates a computer or network without a user's knowledge or permission, often disguised as innocent, and can cause harm, such as stealing the user's personal information, accessing sensitive data, crashing the system, or participating in attacks through the user's system. Unlike a virus, it cannot replicate or infect files on its own.

What are the Types of Trojan Horses?

Backdoor Trojan

A backdoor trojan virus creates a hidden communication channel that allows the attacker's command and control center to remotely control the infected device. malware is the type. This could allow hackers to steal data, monitor user activities, and distribute additional malware. Backdoor Trojans are a particularly dangerous type of malware because they can provide an entry point for other types of malware or make your computer vulnerable to attack. They are often used to set up botnets, where attackers can control a network of compromised devices for malicious purposes without the user's knowledge. Backdoors can also enable attackers to run code and commands on your device or monitor your web traffic without your permission or knowledge.

rootkit

Rootkit trojans work by gaining root or administrative access to a computer by booting with or even before the operating system. This makes them difficult to detect and remove. Rootkits are designed to hide certain objects or activities on your system. Usually their main purpose is to prevent malware from being detected and extend the time it can run on an infected computer. Therefore, rootkits are a powerful tool that hackers can use to disguise and control their other malware. Rootkits are very difficult to detect and remove and often require special software or expert technicians. To prevent rootkit attacks, you should keep your security software updated regularly and avoid downloading software or files from untrusted sources.

DDoS Trojan

It is a type of trojan whose purpose is to initiate Denial of Service (DoS) attacks. It overloads the targeted server's bandwidth and other computer resources, making it inaccessible to others.

Banker

It is a type of Trojan horse that aims to capture your online banking transactions, credit card information and payment systems.

ransomware

Trojan horses that infect the system encrypt all data on the computer, opening a back door to viruses that demand ransom. In this way, the attacker aims to get a ransom from the victim.

How is a Trojan horse transmitted?

Trojan horse viruses can infect computer systems through many different methods. When a Trojan horse virus infects your device, new windows may spontaneously open in your operating system and unexplained disk errors may occur. Additionally, your computer may run slower than before and show strange DLL errors like pop-ups. Your browser's settings, such as home page or start page, can also be changed. These symptoms may be signs that your computer is infected with a trojan virus. Therefore, when you encounter such symptoms, it is important to intervene quickly by scanning your computer and taking necessary measures.

1. Email Attachments: Trojan horse viruses can spread through email attachments. Malicious individuals use various traps to encourage users to click on email attachments. After opening email attachments, a Trojan horse can infect your computer.

2. Harmful Links: Trojan horse viruses can spread through links that redirect users to malicious websites. These websites may attempt to obtain personal information by redirecting users to a fake login page.

3. Spam Emails: Malicious people can spread the trojan horse virus through spam e-mails. The content of these emails is often prepared to encourage users to click by presenting a fake campaign or offer.

4. Social Engineering: Social engineering is a frequently used method for the spread of trojan virus. By tricking users into checking something like a fake social media account, an online store, or a bank account, malicious actors can infect their computers with the Trojan.

5. Updates: Some trojan viruses can spread through seemingly trustworthy sources, such as computer system or software updates. By offering a fake update, malicious actors may encourage users to download the Trojan virus onto their computers.

How to remove Trojan horse (trojan) from computer?

• Disconnect your computer from the internet: Disconnecting your computer from the internet will prevent the Trojan virus from contacting the command and control (C&C) server and potentially downloading additional malware or sending sensitive information.

• Defender for Windows devices: Windows Defender is an antivirus and security software integrated into Windows operating systems. This software helps protect users against malware such as Trojan viruses by providing a basic level of security. Since Windows Defender is directly integrated with the Windows operating system, you do not need to install extra software. Security software and virus definitions are automatically updated through Windows Update. Windows Defender uses low system resources and does not affect your computer's performance.

Windows Defender can provide adequate protection for daily use and be effective against malware such as Trojan viruses. However, if you are looking for a higher level of protection and additional security features, third-party antivirus software (e.g. Norton, Kaspersky, Bitdefender, etc.) may be more suitable. These software often have advanced threat detection and blocking capabilities, secure payment protection, and more customizable security options.

• Download and install up-to-date antivirus software: If you do not have antivirus software installed on your computer, you need to download and install an updated antivirus software. The antivirus software will scan your computer and detect the trojan virus. When you disconnect the computer from the internet to prevent the spread of the virus, you will not be able to download the antivirus program. To do this, you can install an antivirus program by downloading it from another device and moving it to a computer that is disconnected from the internet.
  • Choose a reliable antivirus program on the device with an internet connection.
  • On the official website of the antivirus software, you usually click on a link button such as “Download” or “Download”.
  • Using a portable storage device such as a USB memory stick or external hard drive, move the installation file of the antivirus program you downloaded to the device that is disconnected from the internet.
  • You can start the installation by connecting the portable storage unit to a computer without an internet connection and selecting the installation file of the antivirus program. You may need to restart the computer when the installation is complete.
  • When you re-establish the internet connection, you need to update the antivirus program. Antivirus software works based on constantly updated virus definitions and it is important that they are up to date.

• Start your computer in safe mode: By starting your computer in safe mode, you can prevent the Trojan virus from functioning normally.

Safe mode startup for Windows computers: 

1. After turning on your computer Settings Open the menu. From here Update & Security Go to section.
2. Open the recovery menu. Recovery options from Advanced Startup Click .
3. Restart Restart your computer by clicking the button. In this way, your Windows 10 computer will be opened in safe mode.

Safe mode startup for Mac computers:

Mac with Apple Silicon chipstarting in safe mode

1. On your Mac, choose Apple menu > Shut Down.
2. Press and hold your Mac's power button until “Loading startup options” appears.
3. Select a disk partition.
4. Hold down the Shift key, then click Resume in Safe Mode. The computer restarts automatically. When the login window appears, you should see “Secure Boot” in the menu bar.

Intel-based Macstarting in safe mode

1. Turn on or restart your Mac, then immediately hold down the Shift key until you see the login window.
2. Sign in to your Mac.
3. You may be asked to sign in again. On the first or second login window, you should see “Secure Boot” in the menu bar.

• Delete suspicious files and programs: Select Control Panel > Programs > Features. Check for any suspicious files or programs among your recently installed applications and remove them from your computer after checking them.

• Delete the Trojan: You can use "Trogen Remover" programs to remove Trojan horse virus. These programs find and clean harmful software and files on your system.

• Restore your system to its previous state: If the Trojan horse virus has caused significant damage to your computer system, you can restore your system to a previous state or perform a backup to recover your data. Restoring the system to its previous state on Windows and Mac computers is done by different methods.

You can restore the computer to a previous state using the system restore feature in Windows.

1. start Click on the menu and "Control Panel" in summer.
2. In Control Panel “System and Security” Click .
3. "System" Click .
4. System protection select and "System features" in the window System Restore Click the button.
5. Select the date and times you want to revert to a previous point by following the System Restore wizard. The wizard will guide you through the steps required to complete the restore.

Note: Previous restore points must be created for System Restore to work.

On Mac computers, restoring to a previous state is accomplished using Time Machine backups. You must have created a Time Machine backup beforehand.

1. Shut down the Mac.
2. Turn on Mac and Command (⌘) and R. pressing the keys simultaneously macOS Recovery mode open. The Apple logo will appear followed by a spinning globe icon or macOS utilities window.
3. “Reinstall macOS” or "Reload" Click .
4. Select the dates and times you want to restore using the Time Machine backup and wait for the restore process to complete.

• Update your computer: Update all programs on your computer, including software and operating system. This helps make your computer more secure and provides better protection against Trojan virus in the future.

What are the damages that Trojan viruses can cause in your business?

Data theft: Trojan virus is designed to steal your business' sensitive data. It includes customer information, financial information, business secrets and other important information. Trojans can cause serious damage to your business by stealing this information.

System damage: Trojans can damage business systems, preventing systems from working properly by deleting or modifying important files.

Data encryption and ransomware: Some Trojans are used as a tool to install ransomware. Ransomware encrypts business data, denying users access and demanding payment to restore the data.

Taking control of computer systems: A Trojan horse virus can take control of your business's computer systems. This can cause damage to all of your business's computer systems and halt your business' operations.

Sending spam: Trojan virus is used to send spam from your business email accounts. This can damage your business's reputation and cause you to lose your customers' trust.

DDoS attacks: Trojan viruses can infiltrate a computer system or network and perform a variety of malicious actions. The Trojan virus itself does not directly perform a DDoS (Distributed Denial of Service) attack, but computers taken control of using Trojans can be used in DDoS attacks.

Thanks to Trojan horse viruses, cyber attackers can include the computers they have captured into malicious networks called botnets. A botnet consists of many infected computers under the control of cybercriminals, and a DDoS attack can be launched on target systems with the simultaneous and intense traffic flow from these computers.

DDoS attacks can cause target systems or networks to be out of service, which can lead to serious problems for businesses and web services.

Financial damage: Fixing problems caused by Trojan horse viruses and restoring systems can be costly. Additionally, businesses may suffer economic losses due to disruptions in business processes and loss of customers.

What precautions should you take to prevent Trojan horses from infecting your computer?

Use firewall: Use strong and configured firewalls to limit access to your business network and servers. You should regularly update firewall rules to monitor and control internal and external network traffic.

Use up-to-date antivirus software: Install up-to-date antivirus and antimalware software on all servers and network devices. Make sure software is kept updated and runs regular scans.

Follow updates: Close security vulnerabilities by regularly updating operating systems and software running on your servers and network devices.

Network segmentation: Limit the impact of potential malware attacks and control access to sensitive data on your network by segmenting your network.

Access control: Implement authentication and authorization policies by limiting users' and system administrators' access to network and server resources.

Content filtering and email security: Prevent the spread of Trojan viruses through email by using content filtering and secure email gateways in the email services used by your business.

Check out their login page: Some Trojan viruses attempt to steal your personal information through fake login pages. Therefore, make sure that the page is trustworthy, especially when logging into sites that require sensitive information such as banking or financial transactions.

Monitoring and event management: You can react quickly to potential threats by using continuous monitoring and event management systems on your business network and servers.