Keep your Norton Anti-Virus updated.

Norton Anti-Virus 9.x/10.x Defs are the latest anti-virus detection files.

The installer will automatically update Norton AntiVirus for Mac virus definitions and engine files to detect and repair the most recently discovered Macintosh viruses. This file is a self-extracting archive which contains the Norton AntiVirus Virus Definitions Installer.

Once downloaded and expanded on your hard drive, simply double-click on the Installer and the appropriate files will be installed on your computer.

They are also available via the LiveUpdate feature in Norton Anti-Virus 9.x/10.x