What is a Trojan Horse?

What is a Trojan Horse?

In the computer environment, a Trojan horse is a program that disguises itself as a useful application. Apart from the obvious functions, it has hidden functions that are executed unnoticed by the user. These can be harmful actions such as opening backdoors or downloading more malware.

In the computer environment, the terms Trojan horse or Trojan stand for a computer program that pretends to be a useful application, but has hidden functions unknown to the user. These are executed in the background without the user's knowledge and can be malicious in nature. Trojans are categorized as malware and unwanted software, although the hidden functions may not always be harmful. The Trojan differs from a virus in that it acts as a host for the actual malicious code and can, in principle, inject any type of code. A Trojan horse does not have the mechanisms that contribute to self-propagation.

Trojans are often installed by users themselves, under the assumption that it is a normal application. Once installed, the Trojan horse opens backdoors to reload malicious code or runs malicious programs such as keyloggers. The so-called "federal Trojan" is a Trojan intended to be used for online searches in cases of serious crime in law enforcement or security.

The origin of the name of the Trojan Horse

The name is derived from the mythological tale of the Trojan War. It is said that a wooden horse was used, which the besieged inhabitants of Troy voluntarily let into the city, and inside it were fighters of the Greek besiegers. Through this ruse, the city was captured.

Possible harmful functions of a Trojan

Different types of data

Source: Wikipedia

A Trojan can host any malicious or innocuous functions. For example, Trojans with malicious code perform the following hidden functions:

  • opening a backdoor on the computer to give hackers access
  • the stealing of data
  • the reloading of further malware
  • the takeover of control by a hacker
  • the integration of the computer into a botnet
  • the execution of distributed denial of service (DDoS) attacks
  • the recording of user input (keylogger)
  • the reading of the data traffic
  • spying on user IDs and passwords
  • the deactivation of anti-virus programs or the firewall
  • the installation of dialer programs
  • the display of unsolicited advertising
  • the encryption of data and extortion of ransom money (ransomware)
  • the use of computer resources for third-party purposes, such as mining digital currencies

Protective measures against Trojans

To protect themselves against Trojans, users need to be made aware. They should never install software unknown to them or programs from dubious sources on the computer, even if they claim to perform useful functions. Downloading software on the Internet should only be done from trusted sites. In addition, the usual measures against malware must be taken, such as the use of up-to-date antivirus programs and firewalls. Regular updates and patches must be applied to the operating systems and applications used. Caution is also advised with e-mail attachments containing executable files (.exe files). Malicious programs or Trojans may also be hidden in other file types.

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