A Trojan Horse is a program that uses malicious code masqueraded as a trusted application. The malicious code can be injected on benign applications, masqueraded in e-mail links, or sometimes hidden in JavaScript pages to make attacks against vulnerable internet Browsers.

TYPES OF TROJAN HORSE

1.Remote Access Trojan(RAT):
It Provides full control of the infected machine to the attacker.Trojan Horse usually masqueraded as a utitility.
2.Data Sending Trojan:
It uses keylogger technology to capture useful data such as passwords,credit card and banking information
and sends them back to the attacker.
3.Destructive Trojan:
it is designed to destroy the data stored on the victim’s computer.

4.Proxy Trojan:
It uses 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.

5.FTP Trojan : It uses port 21 to enable the attackers to connect to the victim’s computer using File Transfer Protocol.

6.Security software disable Trojan:It is designed to disable security software like firewall and antivirus,it enables the attacker to use many invasion techniques to invade the victim’s computer.

7.Denial-of-Service attack Trojan:It is designed to give the attacker opportunity to realize Denial-of-Service attacks from victim’s computer.

SYMPTOMS

1.Wallpaper and other background settings auto-changes
2.Mouse pointer disappears
3.Programs auto-loading and unloading
4.Strange window warnings, messages and question boxes, and options being displayed constantly
5.e-mail client auto sending messages to all on the user’s contacts list
6.Windows auto closing
7.System auto rebooting
8.Internet account information changing
9.High internet bandwidth being used without user action
10.Computer’s high resources consumption
11.Ctrl + Alt + Del stops working
12.computer slows down

A Trojan horse can break through all security polices in a network, because an attacker can get access to a WorkStation with stored network credentials. With these credentials, an attacker can compromise the whole network.