The Department of Justice's Executive Office of the U.S. Attorneys has its own file exchange site called USAfx. See: http://usafx.justice.gov . In order to access the site you need to receive an email from a USAO asking you to register your account.
When a USAO chooses to share a folder on its network with defendants at a private law firm, they should receive an email like this one:
As you can see the government's system utilizes the popular cloud file sharing service box.com. The recipient simply needs to access the folder, and then right click on the box.com on the subfolders or files inside and download the contents to a zip file.
Multiple files or folders can be downloaded at once.
The files can only be made accessible for a maximum of 60 days.
The rumor is that it may not be advisable to use USAfx for more than 5 GB or more than 800 files. See this edition of the Federal Defender Newsletter.