What is the Trojan Horse Virus in Computer?

The Trojan Horse virus is a program created and running under a harmless and beneficial dimension for the user, adding a module that can destroy data negatively affects the system. It is one of the best-known and most widely used types of malicious programs, along with other viruses.

What is the Trojan Horse Virus in Computer?

What is Trojan Horse?

It is a program that usually performs one or more functions a user wants and does not want, does not hide, perform unknown actions, and reminds the Greeks’ entry to the protected city of Troy.

They differ from other viruses because secondly, the host program infects any program on the computer that has nothing to do with the virus. Also, unlike other viruses, Trojans do not usually reproduce.

Trojans are generally thought to be less dangerous than worms because they cannot usually be reproduced or transferred.

This is a false statement because most existing malicious programs combine various mechanisms, and most worms have Trojans. Therefore, trojan viruses become more specific.

Many of these programs are keyloggers that send data about keys pressed to the program’s author or user. More complex versions provide nearly full control over victim computers, send their data to remote servers, and receive and execute instructions.

Sometimes infected computers are grouped in a zombie network and, with a certain continuity, use instant messaging channels or websites where new instructions are sent.


The Trojan virus is often used to steal information, to gain remote control of the computer in extreme cases, so the attacker can perform operations such as read and write access to stored files and private data, open screenshots, enable and disable processes.

Computers affected by Trojan viruses become remote workstations that can be managed by the attacker.

In some cases, they limit their use to stealing access codes to services such as IRC, FTP, HTTP, mail, or saving typed characters to find possible keywords that can later be used in fraudulent acts.

The Trojan software can be used to initiate DoS (Denial of Service Attack) to victims whose affected computers are usually Internet or mail servers.

Traces left by these attacks appear on computers where they were started, so users can be charged with unprocessed crimes.

There is also some code designed to disable antivirus and firewalls, so affected computers are more susceptible to new attacks.

Its procedure is due to the addition of an unauthorized code that performs unwanted and unknown actions.


   Back Doors

It is the most dangerous and common method used to attack the back doors. They are utilities with remote administration and they place infected computers with external control over the local network or the Internet.

This method is similar to the remote management programs used by system administrators, making it difficult to detect, these backdoors are installed without the user knowing and consent, when operated, monitor the system without detecting the user, and the victim’s equipment remains at the attacker’s disposal.

   Password Theft

It is a method that usually aims to enter the victims’ computers, search for system files containing private information such as passwords and Internet accounts, and then send this information to an e-mail address.

The captured information is used by the user of the offensive or illegal program.

A Trojan software briefly aims to steal system configurations, IP addresses, registration information, and online website or game passwords.


They send other users’ computers to specific websites or Internet resources, as well as send specific instructions to browsers or change system files where Internet addresses are stored.

They are often used to direct the victim to an infected source, where they will be attacked by other malicious programs or attack the server or a particular website.

   Installing a Program

Programs that download and install new malicious programs on another user’s computer.

A downloader application that downloads the malicious software then executes new malicious programs or saves it to be executed automatically in accordance with the requirements of the local operating system.

This is done without the user’s consent and without the user’s account.


It acts like a proxy server and provides anonymous access to the Internet from victims’ computers.

How Trojan Viruses Work?

They were originally created by a component that contains all the functions associated with the loss of information placed in a commonly used program and stored on hard drives.

Currently, these programs consist of two components, server, and client.

The first is the type of virus that is secretly installed on the affected PC and is usually copied to disk and creates conditions to be executed each time the system is started.

The server can secretly open the communication ports and stay in the listening state to receive requests received by the client remotely from anywhere on the Internet.

The client is a component that runs on the attacker’s PC and uses it as a means to send it to the server and consists of a window similar to many applications we generally know.

How Is It Transmitted?

The most common ways are email attachments, real-time speech and instant electronic messaging, transferring files, downloading free or unknown software, mostly from websites, as well as shared resources on a local network.

In addition, email client applications and Internet browsers allow code contained in HTML format messages to be executed simply by opening.

Email is widely used, so it is very easy for an attacker to enable the recipient to open and run an attached file because they only need to give the sender the name or address of a known person and the appealing text.

Attachments can often refer to games, screen refreshers, greeting cards, and have extensions that can be executed or correspond to duplicate files.

How Is It Detected?

When your computer gets infected with a virus, it can be detected with various symptoms, depending on the code of the virus.

For example, the display of windows with unusual messages on the screen of your computer, the files are visible and hidden, unusual behavior in the computer’s operation, slow operating system, constant system crashes or sudden restarts without knowing the system causes are programs that start automatically.

In addition, we can give examples of the home address changes in your web browsers such as Explorer, Firefox installed on your system and the e-mail messages in your e-mail account.

How Is It Protected?

There are basic protection measures that can be applied without having the extensive technical knowledge to protect viruses in general.

  1. Do not run programs of unknown origin.
  2. Analyze a file or program sent or downloaded with the help of antivirus programs.
  3. When a message with an attachment is sent to your e-mail account, if you do not know the exact source of this mail, do not open this message.
  4. Do not download applications from unsafe sites.
  5. Note that the social network applications you use on your computer or mobile cell phone are up to date and do not forget to update such applications at all times.
  6. Resolve vulnerabilities by always installing updates on your operating system.
  7. Analyze your system using applications that let you know the use of ports.
  8. In addition to antivirus programs, install a firewall application, and apply additional security to your system.

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