One simply view.

 Unfortunate that there are software programmers out there with malicious intent, but it is good to be aware of the fact. For one better protect install one anti-virus and anti-spyware.

The programs designed to damage or do other unwanted actions on a computer system are malwares.

Malware - Short for "malicious software".

                                                                         MALWARE
                                                                     /           |          \
                                                               Trojan   Virus   Spyware
                                                                               (Worms)


Trojan, are software programs that masquerade as regular programs. These programs can do malicious things.

Virus, Worms, dificult to detect because they are typically invisible files, can cause damage on a computer's.

Spyware, can gather data from a user's system without the user knowing it.