In most cases spywares are distributed through freeware and shareware software that are available for free download. Peer to peer file transfers that are so common these days are also used to deliver spywares to a computer. Once the program that also contains the spyware as embedded program is installed in the system, the spyware also gets installed. In that way the user installs the spyware in his PC without being aware of the spyware. If you have a spyware detector installed in your PC, the spyware scanner will warn you of the malware when you are going to install the program.
Spyware in mostly used to gather the data of the internet browsing habits of the user. These data are either used by the spyware author or they are sold to third parties in most cases to online advertising companies. They analyze these data to determine the interest areas of the user and then show targeted advertisements to the user that matches his interests. So, with a spyware installed in your system you are most likely to get frequent advertisements and pop ups when you are online. Apart from interrupting your work, the spywares also block your system resources as they use the memory of your computer and the bandwidth for transferring collected information. This makes your system slower and reduces the speed of the internet connection. With a spyware detector you can successfully detect the spyware programs and remove spyware that will ensure better performance of your PC.
To keep your PC free from spywares you have to download any spyware detector software from the internet. The spyware cleaner software will clean traces of spyware as well as protect your system from further attacks of spyware when you are online.