I am sure you must have heard a lot of these jargon spyware,virus,malware,adware etc. I am sure many of us doesn't know what these exactly mean...
Spyware is a jargon used for denoting advertisement supported software. Once if it finds the way into your system in the form of AcitveX control or so-called "shareware/freeware" software it continuously opens annoying popup windows.
If you would like to protect yourself from these then install only trusted applications and ActiveX controls. When you are busy browsing you will see notifications with "Install" warning, make sure you know what you are installing.
Spyware is essentially a form of adware which not only brings up pop-up ads but also continuously monitors and sends your PC activity to some remote server and effectively hijacking your privacy.
Trojan Horses are the most vulnerable programs which opens-up your computers to bad hackers who effectively take control of your PC (ofcourse they would make sure your machine is rendered unusable).
These are relatively new form of threat. Once spyware/torjan horses gets installed in a computer it can create dialers or change phone number of your dialers to high premium rate numbers and resulting in high phone bills.
In Phishing, fraudulent websites are designed to deceit users to extract sensitive information including credit card, social security numbers etc. In order to attract traffic to their websites they use spoofed emails and indirect weblinks. So beware!
Pharming is another "flavor" of phishing to deceit users they steal the identity of popular institutions like banks, online retailers, etc.
How to protect your self?