1.2 What is a Trojan

Trojan horses are (as their name suggests) programs that do things that are not described in their specifications. The main difference between Trojan-type programs and the real viruses is that they do not replicate themselves. Therefore they do not have the ability to attach themselves to an existing legitimate program, in other words they do not have the ability to infect a file: they infect the system.

Trojans can be divided into the following subcategories:

1.2.1. Backdoors: once launched, they can allow someone to take control of another user's PC via the internet, without the user's knowledge.

1.2.2. Passwords stealers: these are programs embedded in files and they steal passwords. These are sent to the maker of the program, without the user's knowledge.

1.2.3. Logical bombs: these Trojans perform some destructive or security-compromising activity whenever specified conditions are met.

1.2.4. Denial of Service tools: these programs send special arrangements of data to a target (usually a web site) with the specific intent of interrupting that target's Internet service.

Virus Science