Safer Networking's Spybot Search & Destroy aims to provide free real-time protection against spyware. However, its version number hasn't changed since we reviewed the product a year ago; and based on recent tests, the program no longer provides good spyware protection.

Spybot passed all of our false positive tests, correctly detecting legitimate toolbars and 6285 other sample files. It did reasonably well in our behavior-based tests, too, correctly detecting critical system changes, additions to the HKCU and HKLM 'Run' keys (which spyware programs commonly target), and alterations of the default Internet Explorer home and search pages and the Hosts file (which can redirect URLs to malicious sites). But Spybot did not detect additions to the startup folder, which can be used to launch spyware applications at boot time.

Spybot detected less than 2 percent of our inactive adware and spyware threats, indicating that its signature database of threats is insufficient. It also failed to detect all nine inactive rootkits. In response to threats actively installed on the PC, it ignored three of ten active adware threats and four of ten active spyware threats. Finally, it failed to disinfect the files and Registry entries of any of the active adware and spyware threats.

Spybot is easy enough to install and use, but its interface is somewhat complicated, with many check boxes to handle various tasks. And because it lacks an auto-update feature, you'll have to reach out for signature updates manually.

For a free program it does offer impressive behavior-based protection. Its ResidentTeaTimer watches for changes to the Windows Registry and other critical system areas, while its SDHelper and Immunize layer blocks Internet Explorer ActiveX exploits and other malicious downloads. Tech-savvy folks will appreciate that Spybot lists Browser Helper Objects (BHOs) and ActiveX controls installed on your PC and that it can securely delete files as well.

Safer Networking does not offer telephone support, but we were impressed with the quality of Web-based support on the company's forums, where dedicated fans answer questions on everything from false positives to the complexities in the software's feature set.

For many years, this freeware program was the antispyware standard, but, regrettably, it is no longer competitive.