The government's simpler security classifications, updated for the digital age, are now being used by Whitehall.
The new classifications, which came into effect on 2 April, are intended to be easier to understand and allow the government to buy standardised, rather than expensive, bespoke, IT. They are part of the government's civil service reform programme, which is designed to reduce bureaucracy.
"We have changed a security classification system that was designed decades ago and introduced a new system fit for the digital age. It will make it easier to share information and save money," said Cabinet Office minister Francis Maude.
"There has been a tendency to over-mark documents rather than to manage risk properly.
Instead of six levels of security (unclassified, protect, restricted, confidential, secret and top secret) that were designed when only hard copy documents were around, there are now just three - Official, Secret and Top Secret.
Most public sector information - around 90 percent of government business - is classed as Official. This includes routine government businesses, public service delivery and commercial activity.
The next level, Secret, is for very sensitive information that requires heightened protective measures. For example, where compromising this could seriously damage military capabilities, internal relations or the investigation of a serious organised crime.
The most sensitive information requiring the highest levels of protection will be marked as Top Secret. This applies to information that if compromised could cause widespread loss of life or threaten the security or wellbeing of the country, or friendly nations.
More than 700,000 civil servants and military personnel are already using the system, and it will be rolled out to the wider public sector at a later date.
While the simplification of the security classification is meant to make it easier government to choose standard IT services, concerns have been raised that smaller private businesses working with government through the G-Cloud could lose out because there is not enough clarity around the changes.
Peter Groucutt, managing director of G-Cloud supplier Databarracks, said: "The new security classifications are a positive step and should make it easier and faster for Government departments to choose and purchase the right type of service from vendors in the right security category.
"However, in its current form it will only serve to further strengthen the position of the big SIs and take away any advantage that the SME currently holds. In order for public sector departments to really see the benefits that smaller providers can offer, there needs to be more support for SMEs trying to meet changing security requirements set by the government."