What can you do about this bug? You can force an update by unchecking and rechecking the above-mentioned option in the Security System Preferences pane, as detailed in a . When I tested this out, it worked. However, it is not a permanent fix. The next time a definitions update is released, you still won't get it within the expected 24 hour time frame. At least that's the way it has worked for me.

A more convenient alternative (although also not a permanent fix) is to use Safe Download Version, a free app developed by Adam Christianson at the Mac Observer. With this app, simply click its Update Definitions button and the most recent update is installed. Done.

Apple has been a busy beaver with these definitions. As of this writing, they are already up to version 10, with a new update seemingly released every couple of days.

For those of you who want to peer under the hood, here's how all of this works:

The malware definitions list is stored in a file called XProtect.plist. To access this file from the Finder, from the Finder's Go menu select Go To Folder (Command-Shift-G) and enter: /System/Library/CoreServices/CoreTypes.bundle/Contents/Resources/. From the window that opens, scroll down until you find the XProtect.plist file. Double-click it. If you have Apple's Property List Editor installed, it will open in that app. Otherwise, it should open in a text editor. The contents list each malware definition for which Apple offers protection.