With regard to spyware, one of the biggest culprits is free software. Many authors of free software will be spyware or advertising software bundle with the software they provide for free. The reason that they do is because they are paid a commission whenever a user installs spyware, advertising. This allows them to still make money even if they offer you their software free of charge.
Often, it is not yet clear that spyware or adware is installed next to the free software. The author will usually hide the fact profoundly in the end-user license agreement that almost nobody reads. This allows the author to argue that the additional installation has been agreed.
The best way to prevent this type of intrusion is to stay away from free software in total. Since it is not desirable for most people, there are a few exceptions to this rule that are usually safe alternatives. One is a software open source. The Community open source developers has a basis for a very clear to develop free software: they believe that software should be free - free of cost and free of spyware, advertising. The second safe alternative is demonstration of the software versions. Demonstration versions are free, but are also limited in their functionality. Demo version software developers hope that users will be as their software enough to buy a fully functional version of the software.
Another point must be made in the free programs. Many people use file sharing software, such as Limewire, download the "free" versions of the software has been designed to be purchased. It is not only illegal, it is also very dangerous. Often software software, spyware adware, Trojan horses or viruses are shared on these networks and are disguised as legitimate software. Since it is expected that the software would come as a file executable or zip, it is very easy to confuse someone using a wrong file name. These types of downloads should be avoided completely.
Sometimes the temptation to install useful software that costs nothing may be quite high. Unfortunately, what is called free software generally has a price to pay. This price may be in form of intrusive and crippling computer spyware, advertising. Simply to practise caution when the choice of free software and understand the motivations of developers can help prevent unwanted extras installation with this software.
Read more about Virus Protection - best protection against viruses.