Remote Access Trojans (RATs) Designed to give an attacker remote control over a victim’s system. Two well-known members of this class are the SubSeven program and its cousin, Back Orifice, although both are older examples.
Data Sending To fit into this category, a Trojan must capture some sort of data from the victim’s system, including files and keystrokes. Once captured, this data can be transmitted via email or other means if the Trojan is so enabled. Keyloggers are common Trojans of this type.
Destructive This type of Trojan seeks to corrupt, erase, or destroy data outright on a system. In more extreme cases, the Trojan may affect the hardware in such a way that it becomes unusable.
Proxy Malware of this type causes a system to be used as a proxy by the attacker. The attacker uses the victim’s system to scan or access another system or location. The result is that the actual attacker is hard to find.
FTP Software in this category is designed to set up the infected system as an FTP server. An infected system becomes a server hosting all sorts of information, which may include illegal content of all types.
Security Software Disablers A Trojan can be used as the first step in further attacks if it is used to disable security software.