Types of Trojan Horse Viruses Trojan Horses have developed to a remarkable level of cleverness, which makes each one radically different from each other. For an inclusive understanding, we have classified them into the following:
Remote Access Trojans are the most frequently available trojans. These give an attacker absolute control over the victim's computers. The attacker can go through the files and access any personal information about the user that may be stored in the files, such as credit card numbers, passwords, and vital financial documents.
Password Sending Trojans
The intention of a Password Sending Trojan is to copy all the cached passwords and look for other passwords as you key them into your computer, and send them to particular email addresses. These actions are performed without the awareness of the users. Passwords for restricted websites, messaging services, FTP services and email services come under direct threat with this kind of trojan.
Key Loggers type of Trojans logs victims' keystrokes and then send the log files to the attacker. It then searches for passwords or other sensitive data in the log files. Most of the Key Loggers come with two functions, such as online and offline recording. Of course, they can be configured to send the log file to a specific email address on a daily basis.
The only purpose of Destructive Trojans is to destroy and delete files from the victims' computers. They can automatically delete all the core system files of the computer. The destructive trojan could be controlled by the attacker or could be programmed to strike like a logic bomb, starting on a particular day or at specific time.
Denial of Service (DoS) Attack Trojans
The core design intention behind Denial of Service (DoS) Attack Trojan is to produce a lot of Internet traffic on the victim's computer or server, to the point that the Internet connection becomes too congested to let anyone visit a website or download something. An additional variation of DoS Trojan is the Mail-Bomb Trojan, whose key plan is to infect as many computers as possible, concurrently attacking numerous email addresses with haphazard subjects and contents that cannot be filtered.
Proxy/Wingate Trojans convert the victim's computer into a Proxy/Wingate server. That way, the infected computer is accessible to the entire globe to be used for anonymous access to a variety of unsafe Internet services. The attacker can register domains or access pornographic websites with stolen credit cards or do related illegal activities without being traced.
FTP Trojans are possibly the most simple, and are outdated. The only action they perform is, open a port numbered 21 – the port for FTP transfers – and let anyone connect to your computer via FTP protocol. Advance versions are password-protected, so only the attacker can connect to your computer.
Software Detection Killers
Software Detection Killers kill popular antivirus/firewall programs that guard your computer to give the attacker access to the victim's machine.
Note: A Trojan could have any one or a combination of the above mentioned functionalities. Some might also come on USB drives, usually as “Autorun.inf” viruses.
The best way to prevent a Trojan Horse Virus from entering and infecting your computer is to never open email attachments or files that have been sent by unknown senders. However, not all files we can receive are guaranteed to be virus-free. With this, a good way of protecting your PC against malicious programs such as this harmful application is to install and update an antivirus program.