The final file integrity monitoring program I want to mention is called Sonar (www.matterform.com/mac_software/file_security/, $17.95). Like Baseline, it's a friendly, Mac OS X-native application that requires no special skill to use. What sets it apart from the other software in this list is that Sonar watches your file system for changes in real time. It can inform you instantly when a file has changed, instead of waiting for you to perform a time-consuming (manual or scheduled) scan. A related program from the same developer called Yank (www.matterform.com/mac_software/uninstaller, $19.95) can create custom uninstallers to thoroughly remove any software installed on your system, even if it doesn't include its own uninstaller or if its uninstaller misses certain files.