Linux is being showcased as a secure operating system thanks to a partnership between the Cabinet Office and IBM; who is increasingly positioning itself as UK’s leading Open Source and Linux provider.
Based on Security Enhanced Linux and IBM Websphere, the solution is aimed at providing a fool proof environment to both public and private realms. SE Linux is based on Linux and includes Mandatory Access Control where the administrator defines explicit rules about who does what.
Some sources describe it as an internal Firewall. Developed by the American NSA - National Security Agency - it has been quickly adopted and embraced by the open source community.
The project is the brainchild of the Central Sponsor for Information Assurance which is part of the UK Government's Cabinet office, working with various partners within the public and private sectors. Its aim is to foster and encourage a culture of security.
You can learn more about SELinux by reading this unofficial FAQ here.