Other details can be found on Man-in-the-browser attack.
The 7 main types of Trojan Horse
1.Remote Access Trojan (RAT)
Designed to provide the attacker full control of the infected machine. Trojan horse usually masqueraded as a utility.
2.Data Sending Trojan
Trojan horse that uses keylogger technology to capture sensitive data like passwords, credit card and banking information, IM messages, and send back to attacker.
Trojan horse designed to destroy data stored on victim’s computer.
Trojan horse that uses the victim´s computer as a proxy server, providing the attacker an opportunity to execute illicit acts from the infected computer, like banking fraud, and even malicious attacks over the internet.
This type of Trojan horse uses the port 21 to enable the attackers to connect to the victim´s computer using File Transfer Protocol.
6.Security software disabler Trojan
The Trojan horse is designed to disable security software like firewall and antivirus, enabling the attacker to use many invasion techniques to invade the victim's computer, and even to infect more than the computer.
7.Denial-of-Service attack Trojan
Trojan horse designed to give the attacker opportunity to realize Denial-of-Service attacks from victim´s computer.
A list of common symptoms is described in this section.
•Wallpaper and other background settings auto changing
•Mouse pointer disappear
•Programs auto loading and unloading
•Strange windows warnings, messages and question box, and options being displayed constantly
•e-mail client auto sending messages to all user's contacts list
•Windows auto closing
•System auto rebooting
•Internet accounts information changing
•High internet bandwidth being used without user action
•Computer's high resources consumption (computer slows down)
•Ctrl + Alt + Del stops working
A Trojan horse can break througt all the security polices in a network, because a attacker can get access to a WorkStation that can have network credentials stored in. With this credentials a attacker can compromise all the network.