A trojan (or a trojan horse) is a malicious computer program that is used to infect the target PC system and cause malicious activity on it. Usually, such programs are used for stealing personal information, spreading other viruses or simply disrupting computer's performance. In addition, hackers can use them for getting an unauthorized remote access to a compromised computer, infecting files and damaging the system. As soon as a trojan horse infiltrates computer, it starts hiding from the victim. Trojans are very similar to the regular viruses and, therefore, are quite difficult to detect. That's why you should rely on reputable anti-spyware. Originally, trojans are not intended to spread by themselves. However, the recent versions have additional components that can enable their propagation. The activity of each of trojan horse depends on its author’s intentions.

Ways that are used for infiltrating the system

One part of trojans are able to propagate themselves and infect the system without users' knowledge. Others must be manually installed on computer as any other software. In fact, there are five major ways used by such parasites for entering the system.

  • Many trojans are distributed with the help of e-mail messages, file sharing networks and online chats (such as ICQ, AIM or IRC). They can arrive as useful attachments, instant messages, links in emails or the additions of peer-to-peer applications. These trojans have unsuspicious names and, therefore, trick users into opening them. Once the user opens such message, the trojan horse silently installs itself on the system.
  • Some trojans can get into the system using web browser vulnerabilities. Their authors run insecure web sites filled with malicious code or distribute unsafe advertising pop-ups. Whenever the user visits such a site or clicks on such a pop-up, harmful scripts instantly install a parasite. The user cannot notice anything suspicious, as a threat does not display any setup wizards, dialogs or warnings.
  • Trojans sometimes get installed by other parasites like viruses, worms, backdoors or even spyware. They get into the system without user knowledge and consent and affect everybody who uses a compromised computer. Some threats can be manually installed by malicious computer users who have sufficient privileges for the software installation. Very few trojans are able to spread by exploiting remote systems with certain security vulnerabilities.
  • Some trojans are already integrated into particular applications. Even legitimate programs may have undocumented functions like remote access feature. The attacker needs to contact a computer with such software installed in order to instantly get full unauthorized access to the system or take over control over certain program.

Activities that can be caused by a trojan horse

The most of trojan horses are capable of causing such activity:

  • Infecting, corrupting and overwriting files, essential system components and installed applications. They can also destroy the entire system by erasing critical files or formatting hard disks.
  • Stealing financial data, such as credit card numbers, login names, passwords, valuable personal documents and other user sensitive information.
  • Tracking the user and each of the keystrokes he or she enters on a keyboard. Trojan horse can also take screenshots and initiate other activity for stealing specific information. 
  • Sending all gathered data to a predefined e-mail address, uploading it to a predetermined FTP server or transferring it through a background Internet connection to a remote host.
  • Installing a backdoor or activating its own component for letting the remote attacker take over a compromised computer.
  • Dropping other dangerous parasites.
  • Performing Denial of Service (DoS) or other network attacks against certain remote hosts or sending out excessive amount of e-mail messages in order to flood predefined computers.
  • Installing a hidden FTP server that can be used by malicious persons for various illegal purposes.
  • Terminating antivirus, anti-spyware and other security-related software. Trojan horse can also disable essential system services and prevent standard system tools from running.
  • Blocking user's access to reputable websites and security-related resources.
  • Displaying undesirable commercial advertisements and pop-ups.
  • Degrading Internet connection and computer's speed. It can also decrease system's security and can cause its instability. 

Examples of Trojan horses

There are thousands of different trojans. The following examples illustrate how harmful these threats can be.

Trojan.Cryptolocker is a trojan, which has been used for spreading very dangerous viruses called Cryptolocker and Cryptowall. It is believed that this trojan can also be used for the distribution of other malware, such as rogue anti-spyware programs, backdoors and similar threats. It spreads around with the help of fake security message claiming that computer is infected with possible virus. When the user clicks such a message, the trojan enters the system and quietly installs ransomware. In addition, it blocks the system and causes a fake warning message on victim's desktop. You can also download this threat to your computer as a useful email attachment or a pop-up ad that offers updating your Java or Flash Player.

Trojan.ZeroAccess is another seriously dangerous trojan horse, which is also known as max++. Note that there are many versions of this trojan and that they all seek the same aim - to steal people's personal information. Seeking this aim, they record every keystroke of the victim and can also make continuous screenshots. This trojan usually sneaks into the system from various Internet resources such as insecure web pages or peer-to-peer networks, and starts its work without wasting its time.

12Trojan.Win32.Krepper.ab is a very dangerous and extremely destructive parasite, which can cause serious issues related to your PC's stability. Usually, it gets into the system from insecure Internet resources, file sharing networks or online chats. It silently works in background waiting for the specified date to run its payload. On the specified date, Krepper virus can try to affect Windows Registry, deleting several critical system folders and initiate other destructive actions. The parasite detects, terminates and totally disables running antivirus software installed on the target computer. Moreover, the trojan is able to connect to various malicious servers and download other harmful parasites from there.

Removal of Trojan horse and other cyber threats

Trojans work in the same manner as the regular computer viruses and, therefore, should be removed from computer with the help of reliable security software. You should never try to remove a trojan horse from your computer manually because you can lead your machine to a serious issues and system damage. In order to get an ability to scan the system properly and find all questionable components on it, you should install any of these programs: SpyHunter, STOPzilla, Malwarebytes Anti Malware. They have already been approved for their capability to detect various trojans and their components.

Beware that sometimes even an advanced spyware remover can fail to help you in the removal of a particular trojan. Each of these threats is constantly updated and sometimes these updates are added before they are noticed by the developers of anti-spyware software. If one of these recommended tools failed to fix your computer, you can always contact our team and ask for advice. 

Newest Trojans

Eliminate caMyciloP

April 27th, 2016. Description of caMyciloP virus. How does it act on a compromised computer? caMyciloP Trojan is a dangerous computer threat that slithers into PC silently, bashes harmful commands in the background and manages to stay undetected, especially if computer user is not observant enough or does... More...

JS/ScrInject.b removal guide

April 26th, 2016. What should you know about JS/ScrInject.b virus? JS/ScrInject.b virus is a new threat in the category of Trojan viruses. Similarly to other Trojans, such as Trojan.ZeroAccess or 12Trojan.Win32.Krepper.ab , this malicious program enters computers along with other malware programs. Of... More...

Hadsruda!bit removal guide

April 26th, 2016. Be aware: Hadsruda!bit malware poses a threat to your computer Hadsruda!bit virus is a dangerous computer infection related to spyware and malware. We identify this malicious program as a Trojan horse since it spreads in inconspicuous ways disguised as a safe file. Once installed,... More...

DATABASE OF Trojans PARASITES

Total Trojans parasites in our DB: 819


    1
  • "Warning! Fatal error:" wallpaper August 9th, 2011 | No Comments
    "Warning! Fatal error:" wallpaper is a fake alert notice produced by WinCoDecPRO, which is another rogue appli...

  • 12Trojan.Win32.Krepper.ab March 23rd, 2016 | No Comments
    WHAT IS 12TROJAN.WIN32.KREPPER.AB? 12Trojan.Win32.Krepper.ab is a trojan which performs various malicious tas...

  • 1999 Trojan December 8th, 2011 | No Comments
    Although this pest is quite old and obsolete, it is still able to harm several types of old operating systems,...

  • 3B Trojan January 5th, 2005 | No Comments
    Although this parasite is really old and out of circulation, it still is really dangerous trojan, able to dama...

  • 3DStars Trojan June 27th, 2011 | 1 Comments
    There are a wide variety of harmful actions available to this parasite, that's why it should always be treated...

  • 3Trojans February 10th, 2005 | No Comments
    This old joke-trojan, which was written in Quick Basic, doesn't carry any harmful actions. This parasite is on...

  • 3x Backdoor November 15th, 2004 | No Comments
    This backdoor may become a real threat to any system. When 3X Backdoor is run on the specific computer, it giv...

  • ABC Trojan November 15th, 2004 | No Comments
    This pest, which was created in 1998, is a typical trojan horse. Once run on somebody's computer, ABC Trojan o...

  • Abebot April 7th, 2008 | No Comments
    Abebot is a backdoor trojan, which is used to lower internet security settings, but recently the popular funct...

  • Accept.3773 November 16th, 2004 | No Comments
    Being a trojan, Accept.3773 sometimes acts like a virus. As a trojan, spreading itself isn't its main aim, ...

  • AceBot April 26th, 2009 | 2 Comments
    AceBot is a tremendously backdoor trojan, which was designed for performing a lot of different destructive act...

  • AcidReign Trojan December 23rd, 2004 | No Comments
    This parasite, which was written in Java Script, is a tremendously dangerous backdoor. AcidReign Trojan usuall...

  • Acropolis Trojan December 9th, 2004 | No Comments
    There are no doubts about how dangerous this trojan is. Acropolis is always a powerful tool of destruction in ...

  • Adload.blb November 25th, 2008 | No Comments
    Win32.Adload.blb trojan hides its activities well therefore it is difficult to notice and remove. Adload can b...

  • AdminDeathBot November 15th, 2004 | No Comments
    As a combination of backdoor and trojan, AdminDeathBot can perform many harmful actions on the infected machin...

  • Admire Trojan December 23rd, 2004 | No Comments
    Admire Trojan is a backdoor trojan, which usually helps the hacker to perform various actions and, as a result...

  • Adnap Trojan February 16th, 2005 | No Comments
    This malicious program acts by simulating Panda Antivirus and, in parallel with that, trying to connect to var...

  • Adrenaline Worm November 15th, 2004 | No Comments
    Although Adrenaline Worm is acting mostly like worm, it also has enough rights to be called a Trojan. Written ...

  • Aduent Trojan January 5th, 2005 | No Comments
    Aduent Trojan is a malicious downloader, which acts by connecting to anonymous IP and downloading specific par...

  • Agent Trojan October 5th, 2008 | 4 Comments
    This malicious program is a trojan downloader, which usually exploits various security holes for infecting the...

  • Agent.apbg November 25th, 2008 | No Comments
    Agent.apbg trojan puts a computer in a great risk. It allows a remote attacker to gain an access to the compro...

  • Agent.Enu.Dropper December 1st, 2008 | No Comments
    The trojan W32/Agent.Enu.Dropper is a name of dangerous trojan. Parasite may appear in a few names like W32/Pr...

  • Agentdoc.c August 30th, 2006 | No Comments
    Agentdoc.c is a trojan that drops malicious files on the infected computer. Once executed, the parasite opens ...

  • Agentdoc.d August 30th, 2006 | No Comments
    Agentdoc.d is a trojan that drops malicious files on the infected computer. Once executed, the parasite instal...

  • Agobot Trojan December 22nd, 2004 | No Comments
    This malicious program uses its specific algorithms for harming the infected system in various ways. Firstly, ...

  • Ajan Trojan December 23rd, 2004 | 1 Comments
    Ajan Trojan is a password stealer, which uses its specific algorithms for continuous monitoring of user's acti...

  • Aladino Trojan December 23rd, 2004 | No Comments
    This parasite is a truly multifunctional trojan, able to damage the infected system in many way. Firstly, this...

  • Alemod May 10th, 2006 | No Comments
    Alemod is a trojan that infects the wininet.dll file, which is an essential component of the Windows operating...

  • Alerter Trojan December 23rd, 2004 | No Comments
    Although this parasite's name makes it look like innocent prank trojans, like Alerta Trojan, this pest isn't a...

  • Alf Modern Studio November 15th, 2004 | No Comments
    This dangerous backdoor can be a real system security and stability threat. With a wide variety of available ...

  • Algus Trojan December 23rd, 2004 | No Comments
    Algous this parasite's main aim is stealing user's passwords, it can also perform several destructive actions ...

  • Alicia Trojan December 23rd, 2004 | No Comments
    Alicia Trojan is a dangerous backdoor, which usually acts through IRC network. This pest can infect the PC aft...

  • Alpha Trojan December 14th, 2004 | No Comments
    This backdoor trojan is extremely powerful and dangerous, that's why staying protected from it by keeping your...

  • Alporon Trojan November 15th, 2004 | No Comments
    Originated in 2004, this pest already caused serious damage to unprotected systems. As other trojans do, Alpor...

  • Alureon June 17th, 2012 | No Comments
    Trojan Alureon is a trojan horse, which has several variants floating in internet space. It is a bigger trojan...

  • Alysium Trojan December 23rd, 2004 | No Comments
    Alysium Trojan is a backdoor, which sneaks into the system via local networks or e-mail messages from unknown ...

  • Amazon virus July 8th, 2015 | No Comments
    What is Amazon virus? Amazon virus is a dangerous cyber infection, which is used by cyber criminals for illeg...

  • Amri Trojan December 23rd, 2004 | No Comments
    This malicious program usually infects the system from a batch-file from unknown Internet locations or suspici...

  • Anaphylaxis Trojan December 23rd, 2004 | No Comments
    This malicious trojan, which was written in Assembler language, is a very dangerous parasite. It is always abl...

  • Android.Pris July 17th, 2012 | No Comments
    WHAT IS ANDROID.PRIS? Android.Pris is a Trojan horse that is set to infect Android devices. Security exper...

  • Andromeda Trojan March 17th, 2015 | No Comments
    What is Andromeda? Andromeda virus is a dangerous trojan horse, which can be used for lots of malicious ...

  • Androv Trojan January 10th, 2005 | No Comments
    Androv trojan is a malicious parasite, which was written in Russia. This pest usually infects the system from ...

  • Anime Trojan December 23rd, 2004 | No Comments
    This parasite is a macro trojan, which was created with the help of Visual Basic Script. Anime Trojan usually ...

  • Anon Trojan November 15th, 2004 | No Comments
    This trojan horse can cause some real damage to the systems with a low defence level by trying to clean its di...

  • Ansibart Trojan December 14th, 2004 | No Comments
    There are no doubts about how dangerous this parasite is. Once run on the computer, Ansibart Trojan starts dam...

  • Anti-School Trojan November 15th, 2004 | No Comments
    This malicious trojan can do extremely serious damage to the infected system's data. Once run on the computer,...

  • AntiAntivirus December 24th, 2004 | No Comments
    This parasite, as it is clear from its name, specializes in disabling the defence installed on the target comp...

  • AntiExe.e July 9th, 2010 | No Comments
    This trojan has several common features with a virus. Although it doesn't make its copies through e-mails or o...

  • Antigen Trojan December 24th, 2004 | No Comments
    Antigen Trojan is a specific parasite, which was designed with one aim of stealing user's passwords. Once run ...

  • AntiGolded Trojan December 14th, 2004 | No Comments
    This malicious program is a parasitic trojan, which is always a threat for those users, who have no good and r...

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