When you're happy and you know it (and you really want to show it) what do you do if you're a spy at the United States National Security Agency successfully cracking encryption? You draw a stick figure doing a happy dance.

Over the Christmas break, the German Der Spiegel magazine published new disclosures and documents of signals intelligence cooperation between the United States and its "5-eyes" partners – Britain, Canada, Australia and New Zealand – revealing that the secret agencies had broken most widely used forms of internet encryption.

A slide from documents leaked by NSA whistleblower Edward Snowden.

Among priority intelligence targets were virtual private networks (VPNs) – secure computer networks commonly used by large companies and organisations to transfer data between offices, and by consumers to protect their privacy.

But in one of the documents published, "Intro to the VPN Exploitation Process", the NSA celebrated its ability to break into VPNs in an unusual, childish-like way: a spy drew a stick figure doing a "happy dance".