Purple Penelope was a demonstration secure system created by the Defence Research Agency (DRA) in the UK.
Its aim was to show that the security functionality of Windows NT could be extended to support users handling classified information.
Within a security domain access controls are designed to stop users from accessing material without a need-to-know and to prevent them making mistakes when handling classified data, while controls over sharing information between security domains are more stringent and defend against attacks and hold the users to account for their actions.
[5] The main features were a system of discretionary labelling and a trusted path for authorising security critical actions.
[12] Penelope was the name of the wife of Odysseus who tricked her suitors by weaving a burial shroud during the day and unpicking it at night.