A spyware blocker and remover will protect your computer in two different ways. Firstly, there is the real-time protection which blocks all attempts to install spyware. The second function involves scanning your entire computer and removing all existing Spyware. Basic Anti-Spyware programs will sometimes only be able to perform the second function; scanning and removing of Spyware, since this is much easier than blocking Spyware in real-time. You should therefore look for a Spyware blocker and remover when you choose an Anti-Spyware program, since such programs offers more protection than the basic scanning programs. A program of this type will work in a way similar to that of an Anti-Virus program. The Spyware blocker and remover will carefully check all incoming network data and disk files during the actual download. All components known to be Spyware are immediately blocked by the Program. Some Spyware blocker and remover programs will also block attempts to modify the settings of your browser and all attempts to install start-up items. Unlike a Spyware blocker and remover, a simple Spyware remover is easier to construct since it only has to check the contents of the Windows Registry, the installed programs and the operating system files and remove Spyware when found. A high-quality Spyware blocker and remover will therefore keep your computer and your privacy much safer, since Spyware will be blocked "at the gate".

In the beginning, most Anti-Spyware programs were focused on finding existing Spyware in the computer and removing them. As the Spyware problem grew, a better type of Anti-virus program was developed by several companies; the Spyware blocker and remover. One of the first programs of this type was developed by Javacool Software and named SpywareBlaster. It offered real-time protection and was focused on blocking ActiveX-based Spyware, but also capable of noticing and blocking a lot of other types of Spyware as well. It was however focused on the real-time protection, and not on scanning and removing existing files. Later on, other Spyware blocker and remover programs were introduced; programs that combined the blocking and removing functions more effectively. Examples of such Spyware blocker and remover programs are Windows AntiSpyware and Ad-Aware from Lavasoft.

For most users, it is recommended to choose Spyware blocker and remover programs instead of Anti-Spyware programs capable of just one task. Even with a good Spyware blocker and remover program you are however not completely out of harms way. If a Spyware blocker and remover program fails to block a Spyware program, the Spyware can sometimes resist later attempts to delete or uninstall it. Some cleverly created Spyware programs work in pairs. When the Spyware blocker and remover program finds one of the programs and terminate its actions, the other Spyware program will promptly start up the program again. Other Spyware programs are designed to notice attempts to remove Registry keys and can rapidly add the Registry keys again. If you experience such problems with your program, you can try booting your computer in safe mode. This will usually give your Spyware blocker and remover program a better chance of finally getting rid of unrelenting Spyware.