So a user simply has to chose a password and then the PGP system does all of the encryption and makes the file or the message secure.

NPR: The Math Behind Pellicano's Code

They can then enter the recipient or recipients, compose a short message, adjust security settings and send the file.

FORBES: Blue Rooster's 'Madison' Offers Alternative To Dropbox For The Enterprise

The first sign of attack is a message that appears to come from a contact, offering you a file to download.

BBC: Hand on keyboard

Anyone searching for the source code on file-sharing systems will see a pop-up message alerting them to the fact that downloading the code is illegal.

BBC: NEWS | Technology | Microsoft targets source pirates