Beware Of Spies!
•DON’T talk. The enemy has ears everywhere.
•DON’T imagine that everyone who speaks English is to be trusted and that every uniform covers a friend.
•DON’T exchange confidences with casual companions or when traveling at home or abroad.
•DON’T trust strangers who write to you, who offer gifts or hospitality, or who tell you their secrets.
•DON’T carry about with you or show maps, plans, orders, or any naval or military document.
•DON’T hesitate to prevent and to report at once any leakage of information or any suspicious action.
•DON’T mention naval or military matters in your letters. They have a habit of getting into print to the advantage of the enemy.
•DON’T imagine that private diaries or notebooks will keep secrets. They sometimes get lost or stolen.
•DON’T leave written scraps of papers about. Burn them. They might tell tales.
•DON’T forget that a chance word or a scrap of paper may help your enemy and slay your friend.
– John Mackat