It is defined as information that would "damage" national security if disclosed to the public.

Under guidelines laid out for the program, historical records are released except in instances where disclosure would damage national security.

By taking the spy business more seriously, it could avoid the messy scandals that damage security.

"How she chooses to spend her time would not concern me, if it did not have the potential to damage national security," he said coldly.

Parties out of power only threaten to damage national security.

And worse, people like you and me, citizens, clearly only threaten to damage national security when they get involved.

All are kept secret under national security laws on the ground that their release would damage national security.

Any release of secret information in the documents, the subcommittee was told, would seriously damage national security.

They can damage national security, are not in the national interest and, as the US have said, may put lives at risk.

The purpose of classification is to protect information from being used to damage or endanger national security.