Anti-spyware software protects computer users from spyware and other potentially harmful software. Anti-spyware programs protect computers from malicious spyware that attempts to take partial control of or intercept a computer's operation without the user's consent or knowledge.

Anti-spyware software provides real-time protection, as well as scanning and removal. Real-time protection works in the same way that real-time anti-virus protection does. That is, the program monitors all incoming data by scanning all files that the user attempts to download from the Internet, and it blocks the activity of spyware-related components. Real-time protection also prevents unauthorized attempts to install startup programs or alter browser settings. Most anti-spyware programs have simple scanning and removal features. The program scans the contents of the operating system files, Windows registry, and installed programs and removes any entry or file that matches those in the previously identified list of spyware components.

Anti-spyware software also necessitates a frequently updated database of the most recent spyware components. When new spyware is released, anti-spyware developers discover and evaluate it, and then create "definitions" or "signatures" that assist anti-spyware programs in identifying and removing the spyware. As a result, it is highly recommended that the anti-spyware program be updated on a regular basis to ensure protection.

Anti-spyware features have been added to existing anti-virus products by major anti-virus companies such as McAfee, Symantec, and Sophos.

Anti-spyware programs from well-known companies are usually not free to use; however, the manufacturers may occasionally offer a free trial period during which only certain features are enabled. They frequently only offer free scanning; actual spyware removal is only possible with a registered version of the product. Because there are fake anti-spyware programs that are actually spyware, the price of legitimate software and the protection it provides should not deter you.