Types of Trojan Horse Virus ~ Hacks N Cracks

Remote Access Trojans
Password Sending Trojans
Keyloggers
Destructive
Denial Of Service (DoS) Attack Trojans
Proxy/Wingate Trojans
FTP Trojans
Software Detection Killers

■ Remote Access Trojans

These are the Trojans usually seen referred to in the media and hence gain high visibility because of their ability to give the attackers the power to do more things on the victim's machine than the victim itself, while standing in front of the machine. Most of these Trojans are often a combination of the other variations discussed below.

■ Password Sending Trojans

These Trojans are directed towards extracting all the cached passwords and also capture other passwords entered by the victim and email them across to an attacker specified mail address, without the victim realizing it. The password harvest may include passwords for ICQ, IRC, FTP, HTTP or any other application that require a user to enter a login and password. Most of them do not restart when Windows is loaded, as the objective is to gather as much info about the victim's machine as passwords, mIRC logs, ICQ conversations and mail them to the attacker.

■ Keyloggers

These Trojans log the keystrokes of the victim and then let the attacker search for passwords or other sensitive data in the log file. They usually come with two functions such as online and offline recording. As with the previous group, these Trojans can be configured to send the log file to a specific e-mail address on a regular basis.

■ Destructive

The only function of these Trojans is to destroy and delete files. They can deliberately delete core system files (for example: .dll, .ini or .exe files, possibly others) on the target machine. The Trojan is activated by the attacker or sometimes works like a logic bomb and starts on a specific day and at specific hour.

■ Denial of Service (DoS) Attack Trojans

These Trojans used by attackers to issue a denial of service. A distributed denial of service may also be issued if the attacker has gathered enough victims. WinTrinoo is a DDoS tool that has become popular recently, and if the attacker has infected many ADSL users, major Internet sites could be shut down as a result.

Another variation of a DoS Trojan is the mail-bomb Trojan, whose main aim is to infect as many machines as possible and simultaneously attack specific e-mail address/addresses with random subjects and contents which cannot be filtered.

■ Proxy/Wingate Trojans

Underground sites are known to announce freely available proxy servers. These Trojans turn the victim's computer into a proxy/Wingate server available to the whole world or to the attacker only. It is used for anonymous Telnet, ICQ, IRC, etc., and also to register domains with stolen credit cards and for other illegal activities. This gives the attacker complete anonymity and the chance to do everything and point the trail to the victim.

■ FTP Trojans

These Trojans open port 21(the port for FTP transfers) and lets anybody or just the attacker connect to the machine. They may be password protected so only the attacker is able connect to the computer.

■ Software Detection Killers

There are such functionalities built into some Trojans, but there are also separate programs that will kill Zone Alarm, Norton Anti-Virus and many other (popular anti-virus/firewall) programs, that protect the target machine. When they are disabled, the attacker has full access to the machine to perform some illegal activity or use the computer to attack others and often disappear.