Viruses and Trojan Horse

Viruses and Trojan Horses
Viruses and Trojan Horses

In this article we will talk about Viruses and Trojan Horse, and in previous article we already discussed about Authentication with a Local Password.

The first and most common type of computer malware is a virus. Viruses require human action to propagate and infect other computers. For example, a virus can infect a computer when a victim opens an email attachment, opens a file on a USB drive, or downloads a file.


The virus hides by attaching itself to computer code, software, or documents on the computer. When opened, the virus executes and infects the computer.

Viruses can:

  • Alter, corrupt, delete files, or erase entire drives.
  • Cause computer booting issues, and corrupt applications.
  • Capture and send sensitive information to threat actors.
  • Access and use email accounts to spread.
  • Lay dormant until summoned by the threat actor.

Modern viruses are developed for specific intent such as those listed in the table.

Types of VirusesDescription
Boot sector virusVirus attacks the boot sector, file partition table, or file system.
Firmware virusVirus attacks the device firmware.
Macro virusVirus uses the MS Office or other applications macro feature maliciously.
Program virusVirus inserts itself in another executable program.
Script virusVirus attacks the OS interpreter which is used to execute scripts.

Trojan Horse

Threat actors use Trojan horses to compromise hosts. A Trojan horse is a program that looks useful but also carries malicious code. Trojan horses are often provided with free online programs such as computer games. Unsuspecting users download and install the game, along with the Trojan horse.

There are several types of Trojan horses as described in the table.

Type of Trojan HorseDescription
Remote-accessTrojan horse enables unauthorized remote access.
Data-sendingTrojan horse provides the threat actor with sensitive data, such as passwords.
DestructiveTrojan horse corrupts or deletes files.
ProxyTrojan horse will use the victim’s computer as the source device to launch attacks and perform other illegal activities.
FTPTrojan horse enables unauthorized file transfer services on end devices.
Security software disablerTrojan horse stops antivirus programs or firewalls from functioning.
Denial of Service (DoS)Trojan horse slows or halts network activity.
KeyloggerTrojan horse actively attempts to steal confidential information, such as credit card numbers, by recording key strokes entered into a web form.

Viruses and Trojan horses are only two types of malware that threat actors use. There are many other types of malware that have been designed for specific purposes.

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