For example, to block outbound file transfers of proprietary files over FTP, you can create a policy based on keywords or patterns inside the files.
To block outbound proprietary files
Navigate to OBJECT | Match Objects > Match Objects.
Click +Add and create a match object of type File Content that matches on keywords in files.
Optionally, you can create a customized FTP notification action that sends a message to the client.
Click +Add and create a policy that references this match object and action. If you prefer to simply block the file transfer and reset the connection, you can select the Reset/Drop Action Object when you create the rule.