How Dropbox works

Dropbox is designed with multiple layers of protection, distributed across a scalable, secure infrastructure. These layers include:

• Secure data transfer
• Encryption
• Network configuration
• Application-level controls
  
• User-level controls

Here's a diagram of how the service works:

Dropbox users can access files and folders any time from the desktop, web, and mobile clients, or through applications connected to Dropbox. All of these clients connect to secure servers to provide access to files, allow file sharing with others, and update linked devices when files are added, changed, or deleted. The Dropbox service operates various services that are responsible for handling and processing both metadata and raw block storage.