CS406: Information Security

Trojan Horses cannot replicate themselves like viruses and worms. There are seven main types of Trojan Horses:

1. Remote Access Trojan (RAT): They can be downloaded from small files such as free software, games, or electronic greeting cards. Once downloaded, the intruder can gain complete administrative control of the computer gaining knowledge of every keystroke made; which can include sensitive personal information of the user.
2. Data Sending Trojan: Relays sensitive information back to the intruder, such as credit card information, email addresses, log files, and so on. Some are used to relay information and not intended for malicious acts. Instead, they are used to serve ads to the user. Hackers gain data of the user's Web activity and site visited to serve corresponding ads to the user.
3. Destructive Trojan: This Trojan is used to destroy data on the user's computer.
4. Proxy Trojan: Uses the victim's computer as a proxy server. The Hacker can then execute any illegal or malicious act from the user's computer over the internet.
5. FTP Trojan: Installs a File Transfer Protocol (FTP) on the user's machine. The Trojan then opens port 21 to the attacker allowing the system to try to download and upload files from the user's computer.
6. Security software disabler Trojan: Designed to disable firewall and antivirus software allowing the attacker to invade the user's computer.
7. Denial-of-Service attack Trojan: Initially installed through a RAT Trojan. One of the more popular RATs is the SubSeven Trojan from various computers routed to the victim's service. Affected machines are referred to as Zombies. 

Source: https://en.wikibooks.org/wiki/The_Computer_Revolution/Security/Malware
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