For those secure testing environments that do not allow Internet access, you will not be able to directly download/update your threats.
In these instances, you will need to install the Avalanche GUI on another PC with internet access and configure your Avalanche GUI to with your username and password under Tools>Protocol and Attack Updates.
Once you've successfully updated your database, you will need to transfer the C:\Program Files\Spirent Communications\Spirent TestCenter [version]\Layer 4-7 Application\database\threatex\ThreatDB folder and it's contents to a USB key or CD.
From the USB/CD, transfer the folder and contents to the same folder on the secure PC. When you start the Avalanche Commander GUI and go under Client>Actions>Attack Lists and open the Editor for the first time, the GUI will rebuild the database and show the complete list of threats that are available.